• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.383-396
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• 2007

The studies on efficiency of flood control reservoir has been introduced into four categories including direct flood control contribution by reservoir, flow-duration change and environmental-ecological change in downstream of dam and flood damage estimation of flood plain. In spite of all the previous approaches, the quantification of the effect of reservoir on the flood control in planning stage is quite complex due to lack of a standard for quantifying feasibility of project. In this study, we develop a methodology that can clearly and accurately quantify the flood damage reduction together with the existing flood level reduction at downstream. The proposed approach uses three appraisal standards of flood control: 'potential safety', 'relative risk' and 'absolute risk' according to the risk by stage. The developed methodology was applied to the Namhan river basin with the storm event of July, 2006. The result shows the damage reduction of 4,189 billion won was estimated. The economic benefits for the flood control effect by dam will greatly contribute to the public understanding of the importance and the effect of the flood control by dam.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.829-837
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• 2011

A study on the grain size change, sedimentary facies and age indicator of volcanic tephra was analysis through four cores (P1 ~ P4) at the Ulleung Basin in the East Sea of Korea. The two cores (P1 and P2) were collected in the northeastern side of the Ulleung Basin (about 2,000 m in water depth), while the other two cores (P3 and P4) with the water depth of about 1,500 m and 1,700 m, respectively, were collected from the continental slope of the southwestern and western side of the Ulleung Basin. Four sedimentary facies and eight sedimentary subfacies were identified. The four facies were massive sand, bioturbated mud, homogeneous mud, and laminated mud. The eight subfacies were further divided as pumiceous ash massive sand, scorieaous massive sand, plain bioturbated mud, pyrite filamented bioturbated mud, distinctly laminated mud, indistinctly laminated mud, thinly laminated mud and homogeneous mud. The homogeneous mud was not found in the core of P3 which is located in the western side of Ulleung Basin (close to the Korean coast). In the case of laminated mud facies, the thinly laminated mud facies was dominated in the lower part of core sequences of the Ulleung Basin (P1 and P2), while the indistinctly laminated mud were overally distributed in the core sequences from the continental slope of Ulleung Basin. The Tephra layers from the core sequences of central Ulleung Basin were more dominated and distinctive than those from the core sequences of continental slope. This is related to the distance from the volcanic source and the amount of sediment supply. The core locations of Ulleung-Oki Tephra layers in the central Ulleung Basin were in the upper part of core sequences, while those in the continental slope were in the lower part of core sequences. This is indicated that the amounts of sediment supply in the continental slope after the Ulleung-Oki eruption were very high and different sedimentary environment between upper and lower of Tephra layer.

• The Journal of Internal Korean Medicine
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• v.32 no.3
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• pp.345-360
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• 2011

Objectives : This study was examined to investigate the effects of Cheonmagudeng-um gagam (CGG) extract on spontaneous hypertension. Methods : For the study of CGG, we divided rats into three groups. The normal group was Wister Kyoto rats (WKY). The control group was spontaneously hypertensive rats (SHR). The treatment group was SHR which were administered CGG extract (SHR-CGG). SHR-CGG were orally administered CGG extract that was diluted in distilled water at the various concentrations for 4 weeks (234.5 mg/kg) and SHR were orally administered the same dosage of plain distilled water as SHR-CGG. Then we measured anti-oxygen effects, ACE inhibitory activity, weight of heart and kidney, blood pressure, heart rate, plasma aldosterone, electrolyte, creatinine, uric acid, BUN, and observed the cortex of the cardiac muscle, kidney, and adrenal gland. Results : CGG increased DPPH scavenging activity and SOD similar activity depending on the concentration. CGG significantly decreased ROS, TNF-${\alpha}$, IL-6, IL-$1{\beta}$, heart weight, blood pressure, heart rate, aldosterone, and BUN in SHR. CGG increased ACE inhibition activity depending on the concentration. CGG inhibited the heart, kidney and adrenal gland tissue injury that is caused by hypertension. Conclusions : These results suggest that CGG is effective in treatment and prevention of hypertension.

• Journal of Korea Water Resources Association
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• v.33 no.5
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• pp.581-592
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• 2000

Turbulence structure and suspended sediment transport capacity in vegetated open-channel flows are investigated numerically in the present paper. The $\textsc{k}-\;\varepsilon$ model is employed for the turbulence closure. Mean velocity and turbulence characteristics including turbulence intensity, Reynolds stress, and production and dissipation of turbulence kinetic energy are evaluated and compared with measurement data available in the literature. The numerical results show that mean velocity is diminished due to the drag provided by vegetation, which results in the reduction of turbulence intensity and Reynolds stress. For submerged vegetation, the shear at the top of vegetation dominates turbulence production, and the turbulence production within vegetation is characterized by wakes. For emergent condition, it is observed that the turbulence generation is dominated by wakes within vegetation. In general, simulated profiles compares favorably to measured data. Computed values of eddy viscosity are used to solve the conservation equation for suspended sediment, yielding sediment concentration more uniform over the depth compared with the one in the plain channel. The simulation reveals that the suspended load decreases as the vegetation density increases and the suspended load increases as the particle diameter decreases for the same vegetation density.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.153-163
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• 2005

This paper presents two case studies for tunnelling in Bangkok: a subway tunnel site and a flood diversion tunnel site. The first case study is related to ground displacement response for dual tunnel Bangkok MRT subway. The MRT subway project of Bangkok city consists of dual tunnels about 20 km long with 18 subway stations. The tunnels are seated in the firm first stiff silty clay layer between 15-22 m in depth below ground surface. The behavior of ground deformation response based on instrumentation is presented. The back analysis based on plain strain FEM analysis is also presented and agrees with field performance. The shear strain of FEM analysis is in the range of 0.1-1% and in accordance with the results of self boring pressuremeter tests. Meanwhile, the second case study is related to the EPB tunnelling bored underneath through underground obstruction. The Premprachakorn flood diversion tunnel is the shortcut tunnel to divert the flood water in rainy season into the Choapraya river. The tunnel was bored by means of EPB shield tunnelling in very stiff silty clay layer at about 20-24 m in depth. During flood diversion tunnel bored underneath the existing Bangkok main water supply tunnel and pile foundation of the bridge, instrumentation was monitored and compared with predicted FEM analysis. The prevention risk potential by means of predicting damage assessment is also presented and discussed.

• Journal of Korea Water Resources Association
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• v.43 no.9
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• pp.823-833
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• 2010

Open-channel flows with submerged vegetation show two distinct flow structures in the vegetation and upper layers. That is, the flow in the vegetation layer is featured by relatively uniform mean velocity with suppressed turbulence from shear, while the flow in the upper layer is akin to that in the plain open-channel. Due to this dual characteristics, the flow has drawn many hydraulic engineers' attentions. This study compares layer-averaged models for flows with submerged vegetation. The models are, in general, classified into two-layer and three-layer models. The two-layer model divides the flow depth into vegetation and upper layers, while the three-layer model further divides the vegetation layer into inner and outer vegetation layers depending on the influence of the bottom roughness. This study compares the two-layer model and the three layer-model. It is found that the two-layer model predicts better the average value of the velocity and the prediction by the three-layer model is sensitive to Reynolds shear stress. In the three-layer model, the mean flow in the inner vegetation layer does not affect the flow seriously, which motivates the proposal of the modified two-layer model. The two-layer model, capable of predicting non-uniform mean velocity, is based on the Reynolds stress which is linear and of power form in the upper and vegetation layers, respectively. Application results reveal that the modified two-layer model predicts the mean velocity at an accuracy similar to the two- and three-layer models, but it predicts poorly in the case of very low vegetation density.

• The Korean Journal of Quaternary Research
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• v.3 no.1
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• pp.87-101
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• 1989

The development of the Hantan river basin can be divided into three stages. The first stage include the ancient Hantan channel system prior to the Chongokni basalt which yield dates of about 0.6 mya from the K/Ar dating method. During this period the Baekuyri formation was formed. The Baekuyri formation is widely observed under the Chongokni basalt along the current river system. The second stage is the period when stream channels stayed on the top of the basalt plateau. Aggradation and deggradation were continued by meandering and braiding channel systems until major stream channel was formed. The currently remaining deposit on the top of the basalt was formed by lacustrine and fluvial systems in this period. During this period Pleistocene hominid was present on edge of water and flood plain and left Paleolithic material. This period was begun at the time of the final basalt flow dated about 300,000 BP. The third stage is designed for the time when the Hantan river channel was dropped down to a level from which the channel could not influence the top of the basalt any more No more deposit could be formed but erosion by surface water has been continued on the top of the basalt since then. The dropping of the Hantan river channel was probably not very long after the final flow of the basalt. Because of frost action and heavy concentrated precipitation in the basin area along with blocky and clumnar joint structure of the basalt, erosional process of the basalt is believed to have been carried out within a relatively short time. The lowering of the Hantan river channel was probably completed in a cycle of major fluctuation of world cimate. Also, the redclay on the top of the basalt is believed to have been formed during a warm period around 200,000 BP, which accords with the climatic change suggested above fair1y well. The Paleolithic materials in tile deposits fell accordingly into approximately same time period.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.587-596
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• 2011

Ultra rapid-hardening cement is widely used for latex-modified mortar and concrete as repair and finishing material during urgent work. The purpose of this study is to evaluate the improvements in strength made to SBR cement mortars by the adding of various admixtures and by the use of different curing methods. SBR cement mortar was prepared with various polymer-cement ratios, curing conditions and admixture contents, and tested for flow, flexural and compressive strengths. From the test results, it was determined that the flow of SBR cement mortar increased with an increase in the polymer-cement ratio, and the water reducing ratio also increased. The strength of cement mortar is improved by using SBR emulsion, and is strengthened by adding metakaoline. The strength of SBR cement mortar cured in standard conditions was increased with an increase in the polymer-cement ratio, and attained the maximum strengths at polymer-cement ratios of 15 % and 10 %, respectively. The maximum strengths of SBR cement mortar are about 1.8 and 1.3 times the strengths of plain mortar, respectively. In this study, it is confirmed that the polymer-cement ratio and curing method are important factors for improving the strengths of rapid-hardening SBR cement mortar.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.251-258
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• 2018

In construction site, conventional methods such as jackhammer or explosive methods(dynamite) have been often used for the demolition of structures. Use of those methods are more carefully treated in environmentally and historically sensitive area. For those reasons, use of Soundless Chemical Demolition Agent(SCDA) is getting the spotlight. The SCDA is a powder which has expansive strength when it is mixed with water. In these Characteristics, SCDA can destroy the concrete or rock as it is poured into boreholes of the concrete or rock structures. However, there is no industrial standard for the use of SCDA effectively yet. In this study, experimental study to measure the expansive pressure was conducted depending on various boundary conditions such as waterproof, length of the steel pipe, submerged of steel pipe. Furthermore, computational analysis using damage plasticity model to predict the minimum required pressure of the SCDA for the concrete demolition depending on spacing between holes(k-factor) and compressive strength of the concrete was conducted. Obtained results indicates that water heat dissipation with submerged steel pipe shows the stable pressure for measuring the SCDA and hole distance(k-factor) is the most important factor for crack initiation of concrete.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.173-181
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• 2003

This study has evaluated the raingauge network of Nam-Han River Basin by assuming that the rainfall field is homogeneous in space and its spatial correlation structure is exponential. The results of the study was compared with the standard of WMO. Summarizing the results are as follows: (1) The Nam-Han River Basin is not the mountain area, nor the plain area of the WMO standard. However, the correlation length of the downstream part is longer than that of the upstream part, enough to differentiate the rainfall fields in both areas. (2) It seems that the standard for the evaluation of the raingauge network of Nam-Han River Basin should be decided to represent upper 50% of correlations derived, when the maximum intervals between neighboring gauges are estimated to be 18.2km for the upstream area and 21.1km for the downstream area. Simply evaluating the raingauge density, the Nam-Han River Basin has enough raingauges exceeding the WMO standard for the mountain area in the temperate region. (3) Evaluation of the spatial distribution of raingauges in the Nam-Han River Basin shows that its spatial distribution Is not in a proper level, especially when applying the WMO standard for the mountain area in the temperate region. However, when applying the new standard proposed in this study, only five to six more raingauges are required to be added.