• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.1
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• pp.89-99
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• 2006

The growth and biomass of reeds(Phragmites australis) growing in a subsurface treatment wetland system were investigated from April 2003 to October 2003. Nitrogen(N) and phosphorous(P) concentrations in above-ground(AG) and below-ground(BG) tissues of reeds were examined and the removal rate of N and P by reeds were analyzed. The system, 29 m in length, 9 m in width and 0.65 m in depth, was constructed in June 2001 on a floodplain in the down reach of the Kwangju Stream in Korea in order to purify polluted water of the stream. A bottom layer of 45 cm in depth was filled with crushed granites(15~30 mm in diameter) and a middle layer of 10 cm in depth was filled with pea pebbles(10 mm in diameter). An upper layer of 5 cm contained course sand. Reeds were transplanted on the surface of the system, which were dug out of natural wetlands, and their shoots were trimmed 40 cm in height. The height and density of the shoots averaged 237.7 cm and 244.0 shoot/$m^2$, respectively, when the reeds grew fully. The maximum biomass of AG and BG tissues were 1,964 and 1,577 g/$m^2$, respectively, and the AG : BG ratio of biomass was 1.26. Mean AG and BG dry weights were recorded as 1,355 and 748 g/$m^2$, respectively. The AG and BG tissue concentrations of N averaged 12.37 and 10.01 mg/g, respectively, and those of P 2.37 and 2.03 mg/g, respectively. Inflow to the system averaged 40 $m^3$/day. The concentrations of total nitrogen(T-N) in influent and effluent were 8.4 mg/L and 3.2 mg/L, respectively, and those of total phosphorous(T-P) were 0.73 and 0.38 mg/L, respectively. The total removal of T-N and T-P by the system during the investigation period averaged 140.2 and 9.7 g/$m^2$, respectively, and the total uptake of N and P by the reeds were calculated as 24.39 and 4.73 g/$m^2$, respectively. Average removals of about 17% of N and about 49% of P by reeds were recorded. The N and P concentrations in AG tissues were significantly different among the three zones of the system:near to inflow(St1), in the middle of system(St2), and near to outflow(St3). The N and P concentrations in BG tissues were also significantly different among St1, St2 and St3. N and P concentrations in AG and BG tissues of reeds growing in St1 were higher than those in St2 and St3. The height and density of shoots of reeds in St1 were larger than those in St2 and St3. Significant amounts of N and P in the influent were taken up by reeds in St1.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.73-81
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• 2016

In the construction on low strength and high compressible soft ground, the many problems have been occurred in recent construction project. therefore, the soil improvement have been developed to obtain high strength in relatively short period of curing time. Based on the laboratory tests using undisturbed marine clay, the effect of improvement on soft ground was estimated. Deep mixing method by cement have been virtually used for decades to improve the mechanical properties of soft ground. However, previous researches set the focus on the short term strength the about 10% of cement treated clay. In this paper, cement and Natural Soil Stabilizer (NSS) were used as the stabilizing agent to obtain trafficability and mechanical strength of the soft clay. Based on the several laboratory tests, optimum condition was proposed to ensure the mechanical strength and compressibility as the foundation soil using cement and NSS mixed soil. Finally, research data was proposed about the applicability of NSS as the stabilizing agent to soft clay to increase the mechanical strength of soil.

• Applied Biological Chemistry
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• v.15 no.3
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• pp.241-249
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• 1972

The characteristic and efficiency of natural shell sand in the coast of Cheju-Do and Jin-Do were studied to apply as agricultural lime for the soil acid adjustment. 1. The alkalinity of shell sand from Cheju coast was higher than that of Jindo and more weathered into fine particles. The particle size distributions of Cheju shell sand were condensed finer particles than 32 mesh in Cheju shell sands and in more coarser particles than 32 mesh in Jindo one. 2. The effect of Cheju shell sand on increasing soil pH value in the upland condition was low at the beginning but more gradually increased after 8 weeks from the treatment than ground lime, and Jindo was very dull during the period of treatment. The commercial lime crushed from Jindo was approximately equal to the ground lime. 3. In the submerged condition, the shell sand of Cheju reacted with soil acid more quickly than ground lime after 2 days, and Jindo was very slow. 4. The relative efficiency of various particle size fraction of the shell sand was superior to the ground lime. The lime particles between 9 to 14 mesh and 20 mesh had more remarkable difference of pH value than other fine particles. The efficiency among finer sizes than 20 mesh particle was approximately equal to each others. 5. The shell sand from the Cheju would be applied directly as agricultural lime without any treatment, and Jindo also can be expected to be effective as agricultural lime with crushing procedure.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.192-196
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• 2003

Objective of this study was to investigate the influences of harvest index and percolation water quality as irrigated the discharge waters from an industrial and a municipal wastewater treatment plants and seawater (1:5 seawater: tap water) as alternative water resources during tillering stage for drought stress. There were four different treatments such as the discharge water from an industrial (textile dyeing manufacture plant) wastewater treatment plant (DIWT), discharge water from the municipal wastewater treatment plant (DMWT), seawater (1:5) and groundwater as a control. For the initial chemical compositions of alternative waters, it appeared that higher concentrations of COD, $Mn^{2+}$, and $Ni^+$ in DIWT were observed than reused criteria of other country for irrigation, and concentrations of $EC_i$, Cl, and $SO_4$ in seawater were higher than that for irrigation. Harvest index was not significantly different between DIWT and DMWT with different irrigation periods in two soil types, but that of seawater (1:5) is decreased with irrigation periods in clay loam soil and not different between 10 days and 20 days of irrigation periods in sandy loam soil. For percolation water qualities, values of sodium adsorption ratio (SAR) are increased with prolonging the irrigation periods of seawater (1:5) and DIWT, but those of DMWT were almost constant through the cultivation periods regardless of the irrigation period in both soil types. EG of percolation waters is eventually increased with prolonging days after irrigation regardless of irrigation periods in both soil types. Therefore, it might be concluded that there was potentially safe to irrigate the discharge water from municipal wastewater treatment plant relative to harvest index, SAR and $EC_i$ values of the ground water through the rice cultivation period at tillering stage for drought period.

• Journal of Conservation Science
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• v.38 no.1
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• pp.45-54
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• 2022

This study examined the production technique of bracket murals in Daeungjeon Hall, Gaeamsa Temple by conducting a analysis of their wall structure, material characteristics, and painting layers. Wall was a single-branch structure with support layer, middle layer, finishing layer, and painting layer. The support layer, middle layer and finishing layer, were produced by mixing sand (quartz, feldspars etc.), and loess. The ratio of above medium sand to below fine sand was approximately 0.7 : 9.3 in the support layer, 4 : 6 in the middle layer and 6 : 4 in the finishing layer, which had a more percentage of above medium sand than the support layer. The analysis of the painting layer showed that natural soil pigment was used to establish a relatively ground layer of up to 50 ㎛, and pigments such as Lead sulfate, atacamite and mercury sulfide were painted on top of the layer. This study's results confirmed that the bracket mural paintings in Gaeamsa Temple are within the category of the production style of murals during the Joseon period. However, the points that the middle layer was formed several times, the significant difference in particle size distribution between the wall, and the absence of chopped straw in the support layer are a feature of bracket mural paintings in Gaeamsa Temple. These properties of murals as material and structure may be viewed for correlation with the degree of damage to wall structure of mural painting and would serve as an important reference to diagnosis the conservation conditions of murals or prepare conservation treatments.

• Journal of Environmental Impact Assessment
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• v.17 no.1
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• pp.1-9
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• 2008

Non-point pollution is caused by many diffusive sources, unlike a point pollution derived from industrial wastewater treatment plants or sewage treatment plants. Runoff of non-point pollutants is originated from rainfall or thawing in short period of time moving over and through the a ground surface. They cause ill effect on the quality of neighboring aquatic environment. To prevent effectively the wash off from non-point pollutant, it should be immediately reduced at the source or be treated after gathering of runoff water. This study has been carried out for the best width of riparian buffer zone. So we implemented the experiment in terms of its depth, width and kind of vegetations and calculated the reduction of pollutants loading. The experimental zone encompasses the watershed of Namhan River (Kyunggido Yangpyunggun Byungsanri). The region was divided into 5 land cover sectors : grass, reed, pussy willow, mixed(grass+pussy willow) and natural zone to compare effectiveness of vegetation. Water samples from four points have been collected in different depths. And the pollutant removal efficiency by sectors with different plant species was yielded through influent with one of each sample. And we obtained the correlation between the width of riparian buffer zone and the removal efficiency of pollutants. Using correlation result, the width of riparian buffer zones which needs to improve the water quality of river could be derived.

• Journal of the Korean GEO-environmental Society
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• v.16 no.4
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• pp.23-32
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• 2015

This paper addresses the effects of extreme rainfall on the stability of cut slopes in Yen Bai city, Northern Viet Nam. In this area, natural slopes are excavated to create places for infrastructures and buildings. Cut slopes are usually made without proper site investigations; the design is mostly based on experience. In recent years, many slope failures have occurred along these cuts especially in rainy seasons, resulting in properties damaged and loss of lives. To explain the reason that slope failure often happens during rainy seasons, this research analyzed the influence of extreme rainfalls, initial ground conditions, and soil permeability on the changes of pore water pressure within the typical slope, thereafter determining the impact of these changes on the slope stability factor of safety. The extreme rainfalls were selected based on all of the rainfalls triggering landslide events that have occurred over the period from 1960 to 2009. The factor of safety (FS) was calculated using Bishop's simplified method. The results show that when the maximum infiltration capacity of the slope top soil is less than the rainfall intensity, slope failures may occur 14 hours after the rain starts. And when this happens, the rainfall duration is the deciding factor that affects the slope FS values. In short, cut slopes in Yen Bai may be stable in normal conditions after the excavation, but under the influence of tropical rain storms, their stability is always questionable.

• Earthquakes and Structures
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• v.18 no.1
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• pp.27-44
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• 2020

This work presents a comparison of three performance-based seismic design methods (PBSD) as applied to plane steel frames having eccentric braces (EBFs) and buckling restrained braces (BRBFs). The first method uses equivalent modal damping ratios (ξ_k), referring to an equivalent multi-degree-of-freedom (MDOF) linear system, which retains the mass, the elastic stiffness and responds in the same way as the original non-linear MDOF system. The second method employs modal strength reduction factors (${\bar{q}}_k$) resulting from the corresponding modal damping ratios. Contrary to the behavior factors of code based design methods, both ξ_k and ${\bar{q}}_k$ account for the first few modes of significance and incorporate target deformation metrics like inter-storey drift ratio (IDR) and local ductility as well as structural characteristics like structural natural period, and soil types. Explicit empirical expressions of ξ_k and ${\bar{q}}_k$, recently presented by the present authors elsewhere, are also provided here for reasons of completeness and easy reference. The third method, developed here by the authors, is based on a hybrid force/displacement (HFD) seismic design scheme, since it combines the force-base design (FBD) method with the displacement-based design (DBD) method. According to this method, seismic design is accomplished by using a behavior factor (q_h), empirically expressed in terms of the global ductility of the frame, which takes into account both non-structural and structural deformation metrics. These expressions for q_h are obtained through extensive parametric studies involving non-linear dynamic analysis (NLDA) of 98 frames, subjected to 100 far-fault ground motions that correspond to four soil types of Eurocode 8. Furthermore, these factors can be used in conjunction with an elastic acceleration design spectrum for seismic design purposes. Finally, a comparison among the above three seismic design methods and the Eurocode 8 method is conducted with the aid of non-linear dynamic analyses via representative numerical examples, involving plane steel EBFs and BRBFs.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.188-194
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• 2015

River channel dredging and riparian development have been influenced morphology and quantity of natural river habitat. We compared distribution of riverside land and alluvial island in the Nakdong River with field survey and remote sensing analysis after the 4 Large River Project in South Korea. We digitized geomorphological elements, includes main channel, riverside land, and alluvial island by using georeferenced aerial photos taken in pre-dredging (2008) and post-dredging (2012) periods. Field survey was followed in 2012 for a ground truth of digitized boundaries and identification of newly constructed wetland types such as pond, channel, branch, and riverine type. We found that during the dredging period, riverside land and alluvial island were lost by 20.2% and 72.7%, respectively. Modification rate of riverside land was higher in the section of river kilometer 50~90, 140~180, and 210~270. Alluvial island had higher change rate in the section of river kilometer 50~70, 190~210, and 270~310. Average change rate for the riverside land and alluvial island was $-1.02{\pm}0.14km^2{\cdot}10km^{-1}$ and $-0.05{\pm}0.05km^2{\cdot}10km^{-1}$, respectively. Channel shaped wetlands (72.5%) constituted large portion of newly constructed wetlands.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.261-268
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• 2016

Tuned Liquid Dampers(TLD) are energy dissipation devices that have been proposed to control the dynamics response of structure. The TLD has been shown to effectively control the wind response of structures. However, controlling responses of structures with TLD under seismic loads are not fully investigated. The objective of this study is to evaluate the seismic performance of single degree of freedom(SDF) with TLDs having various tuning and mass raitos. For this purpose, analytical studies are conducted. Different soil conditions are considered in this study. As a result, performance of TLD, appeared diffrently depending on the natural period, damping ratio of the structure. Also TLD tuning ratio appeared differently.