• Journal of Korea Water Resources Association
• /
• v.55 no.3
• /
• pp.205-215
• /
• 2022

Amidst the global climate crisis, dam operation policies formulated under the stationary climate assumption could lead to unsatisfactory water management. In this work, we assessed status-quo performance of the Yongdam Dam in Korea under various climatic stresses in flood risk reduction and water supply reliability for 2021-2040. To this end, we employed a decision-centric framework equipped with a stochastic weather generator, a conceptual streamflow model, and a machine-learning reservoir operation rule. By imposing 294 climate perturbations to dam release simulations, we found that the current operation rule of the Yongdam dam could redundantly secure water storage, while inefficiently enhancing the supply reliability. On the other hand, flood risks were likely to increase substantially due to rising mean and variability of daily precipitation. Here, we argue that the current operation rules of the Yongdam Dam seem to be overly focused on securing water storage, and thus need to be adjusted to efficiently improve supply reliability and reduce flood risks in downstream areas.

• The Journal of Engineering Geology
• /
• v.25 no.2
• /
• pp.237-250
• /
• 2015

Underground structures such as a tunnel have been considered as safer than structures on the ground during earthquake. However, severe damages of underground structures occurred at subway tunnel during 1995 Kobe Earthquake and such damages are gradually increased. In this study, a dynamic behavior of a cut and cover tunnel surrounded by weathered soils is investigated using Mohr-Coulomb Model. Parametric study was carried out for boundary conditions, tensile strength, and earthquake magnitudes. The results of numerical analyses in terms of ground deformations and stresses acting on the lining were quite dependent on the side boundary condition (free or fix conditions) and tensile strength of surrounding soils. The ground was deformed upward at the end of earthquake when the side boundary condition was fixed, whereas residual deformations were not predicted when it was free. When the tensile strength of a soil was set to the same as its cohesion, residual deformation was less than 1cm, regardless of side boundary conditions or input accelerations. In addition to that, stress conditions at the maximum deformation and end of earthquake were within an allowable range and considered as safe. Proper boundary conditions and material properties such as tensile strength are quite important because they may significantly impact on the results of dynamic analyses.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.4
• /
• pp.71-80
• /
• 2017

Landscape design pursues a balance among different values in our society, but aesthetic value and ecological value in landscapes must bring complex relationships into harmony. Ecological aesthetics can be defined as a domain of study that manages the relationship between landscape ecology and landscape aesthetics to create aesthetically attractive and ecologically beneficial landscapes. Despite the importance of the research area, there has been limited empirical research addressing ecological aesthetics. This article aspires to connect and expand the conceptual framework to the research methodologies of ecological aesthetics. First, this study suggests a conceptual framework that examines the relationship between landscape and perceptual process in the context of ecological aesthetics. This framework stresses the importance of information and design intervention as moderators in this relationship. From this framework, three key topics in ecological aesthetics arise: (1) correlation between ecological integrity and aesthetic preference, (2) "compromised" design and management intervention principles that enhance aesthetic pleasure and still have biodiversity, and (3) the impact of information intervention in aesthetic experience. The framework indicated three domains affect each other; thus, when one domain is studied, the other two need to be considered. Secondly, several theoretical and empirical studies on ecological aesthetics will be reviewed from a methodological point of view. This will help to consider ecological aesthetics research, which has primarily been limited to theoretical discourse in empirical research.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.35-35
• /
• 2017

How do plants take up water from soils especially when water is scarce in soils? Plants have a strategy to respond to water deficit to manage water necessary for their survival and growth. Plants regulate water transport inside them. Water flows inside the plant via (i) apoplastic pathway including xylem vessel and cell wall and (ii) cell-to-cell pathway including water channels sitting in cell membrane (aquaporins). Water transport across the root and leaf is explained by a composite transport model including those pathways. Modification of the components in those pathways to change their hydraulic conductivity can regulate water uptake and management. Apoplastic barrier is modified by producing Casparian band and suberin lamellae. These structures contain suberin known to be hydrophobic. Barley roots with more suberin content from the apoplast showed lower root hydraulic conductivity. Root hydraulic conductivity was measured by a root pressure probe. Plant root builds apoplastic barrier to prevent water loss into dry soil. Water transport in plant is also regulated in the cell-to-cell pathway via aquaporin, which has received a great attention after its discovery in early 1990s. Aquaporins in plants are known to open or close to regulate water transport in response to biotic and/or abiotic stresses including water deficit. Aquaporins in a corn leaf were opened by illumination in the beginning, however, closed in response to the following leaf water potential decrease. The evidence was provided by cell hydraulic conductivity measurement using a cell pressure probe. Changing the hydraulic conductivity of plant organ such as root and leaf has an impact not only on the speed of water transport across the plant but also on the water potential inside the plant, which means plant water uptake pattern from soil could be differentiated. This was demonstrated by a computer simulation with 3-D root structure having root hydraulic conductivity information and soil. The model study indicated that the root hydraulic conductivity plays an important role to determine the water uptake from soil with suboptimal water, although soil hydraulic conductivity also interplayed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.2
• /
• pp.122-128
• /
• 2005

A feasibility study on the application of self?shielded flux cored arc welding to the on-site SM520 steel bridge box fabrication for express trains and high way construction instead of gas-shield flux cored arc welding was conducted in terms of weld soundness, mechanical properties, toughness and microstructures. All welded specimens made with the self?shielded FCAW process were tested by magnetic particle and ultrasonic techniques and they were found to be sound. All multipass weld specimens made with both self-shielded and gas-shielded FCAW processes showed yield and tensile strengths of $462{\sim}549\;MPa$ and $548{\sim}640\;MPa$, respectively. The impact values of Charpy V-Notch weld specimens also met with the required value of 40J at $-20^{\circ}C$. The hardness values of the top area of weldments were higher than those of the bottom area because of higher residual stresses in the near surface. It was found that welding characteristics of SM520 steel by the on-site welding conditions with self-shielded FCAW showed almost equivalent to those by gas-shielded FCAW in terms of sound welds, mechanical properties and microstructure.

• Microbiology and Biotechnology Letters
• /
• v.33 no.3
• /
• pp.169-177
• /
• 2005

This study focuses on investigating roles of microorganisms in decontamination of reed rhizosphere in Sunchon Bay, Korea, which is considered one of the marsh and mud environment severely affected by human activities such as agriculture and fisheries. In general, the bay is known to play the role of the buffering zone to reduce the sudden impact or change by environmental stresses. In our initial efforts to elucidate the microbial functions in decontamination process in reed rhizosphere, pure bacteria capable of degrading aromatic hydrocarbons were isolated from reed (Phragmites communis) rhizosphere of Sunchon bay by enrichment culture using either benzene, toluene, ethylbenzene, or xylene (BTEX) as a sole source of carbon and energy. Measurement of the rates of BTEX degradation and cell growth during the incubation in BTEX media under several temperature conditions demonstrated maximized degradation of BTEX at $37^{\circ}C$ in both strains. Both strains were also resistant to all the heavy metals and antibiotics tested in this study, as well as they grew well at $42^{\circ}C$. Identification of the isolates based on 16S rRNA gene sequences, and a variety of phenotypic and morphologic properties revealed that the two strains capable of BTEX catabolism were among Microbacterium sp., and Rhodococcus sp. with over $95{\%}$ confidence, designated Microbacterium sp. EMB-1 and Rhodococcus sp. EMB-2, respectively This result suggested that in the rhizosphere of reed, one of major salt marsh plants they might play an important roles in decontamination process of reed rhizosphere contaminated with petroleum such as BTEX.

• Geomechanics and Engineering
• /
• v.21 no.1
• /
• pp.63-71
• /
• 2020

Strength anisotropy is a typical feature of thin-bedded rock masses and their strength will be degraded subjected to water immersion effect. Such effect is crucial for the operation of hydropower plant because the impoundment lifts the water level of upstream reservoir and causes the rock mass of nearby slopes saturated. So far, researches regarding mechanical property of natural thin-bedded rock masses and their strength variation under water immersion based on field test method are rarely reported. This paper focuses on a thin-bedded stratified rock mass and carries out field test to investigate the mechanical property and strength variation characteristics. The field test is highlighted by samples which have a large shear dimension of 0.5 m*0.5 m, representing a more realistic in-situ situation than small size specimen. The test results confirm the anisotropic nature of the concerned rock mass, whose shear strength of host rocks is significantly larger than that of bedding planes. Further, the comparison of shear strength parameters of the thin-bedded rock mass under natural and saturated conditions show that for both host rocks and bedding planes, the decreasing extent of cohesion values are larger than friction values. The quantitative results are then adopted to analyze the influence of reservoir impoundment of a hydropower plant on the surrounding rock mass stability of diversion tunnels which are located in the nearby slope bank. It is evaluated that after reservoir impoundment, the strength degradation induced incremental deformations of surrounding rock mass of diversion tunnels are small and the stresses in lining structure are acceptable. It is therefore concluded that the influences of impoundment are small and the stability of diversion tunnels can be still achieved. The finings regarding field test method and its results, as well as the numerical evaluation conclusions are hoped to provide references for rock projects with similar concerns.

• Korean Journal of Social Welfare
• /
• v.53
• /
• pp.311-336
• /
• 2003

This paper purports to explain the conflicts and compromises between supra-national authority and national welfare state in an era of globalization. For this purpose this paper, first of all, examines if Community law(EU) is directly applicable to member states(direct applicability), and subsequently, if Community law is superior to national law(supremacy). It duly claims that Community law is de facto applicable to member states and thus is superior to national law, but de jure the direct applicability and supremacy of Community law are still ambiguous in practice. Secondly, it briefly describes the development of EU social policy from 'The Rome Treaty(1957)' to 'The Amsterdam Treaty(1997)', and ascertains clear limitations of social dimension of EU. Thirdly, it explains why CEU(Commission of European Union) sequently fails to achieve uniform harmonization policy in the making of social Europe. This paper concludes that 'downward harmonization thesis' or 'convergence thesis' which commonly stresses that globalization seriously impinges on nation-state's policy autonomy and policy capacity is not evidenced at least in the case of EU social policy.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.1
• /
• pp.5-12
• /
• 2016

Investigation of in-situ ground in cold region is difficult due to low accessibility and environmental factors. In this study, correlation between dynamic cone resistance and shear strength is suggested to estimate the strength of frozen soils by using instrumented dynamic cone penetrometer. Tests were conducted in freezing chamber after preparing sand-silt mixture with 2.3% water content. Vertical stresses of 5 kPa and 10 kPa were applied during freezing, shearing, and penetration phase to compare the dynamic cone resistance and shear strength. The dynamic cone resistance, additionally, is calculated to minimize the effect of energy loss during hammer impact. Experimental results show that as the shear strength increases, the dynamic cone penetration index (DCPI) decreases nonlinearly, while the dynamic cone resistance increases linearly. This study provides the useful correlation to evaluate strength properties of the frozen soils from the dynamic cone penetration and direct shear tests.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.22 no.4
• /
• pp.15-34
• /
• 2019

Today, there is increasing recognition of the importance of urban regeneration for better public places. Urban parks as a public area play an important role in harnessing its positive impact on people's well-being: where the standards and funding of/for the parks are getting worse. There is however less a focus on policy approach to park regeneration in the country. Neverthless, a few UK's cases of such innovative park management(PM) has shown successful park regeneration based on policy support. Therefore, the aim of this research is to draw policy implications by exploring a case of successful park regeneration. To address the aim, this research conducts an in-depth case study of 'Manor Fields Park, UK', digging into its PM structure and PM body 'Green Estate Ltd' in relation to relevant policy. The data is mainly collected by interviews including a group interview. The analytical framework 'Place-keeping(PK)' and its six dimensions are employed to determine the characteristics of MFP's PM structure. Resultingly, there is a significant shift in the approach to PM which stresses the principle of long-term and self-sustaining structure led by a non-profit organisation and strong impacts of policy. In this context, PK highlights significant drivers for parks regeneration particularly in terms of policy implications: 1)providing policy support to encourage non-profit organisations in PM, 2)extending community involvement in decision-making processes, 3)promoting income generation by community groups, 4)shifting public awareness of shared responsibility for PM, 5)completing regular park maintenance assessment by community groups, and 6)delivering low-maintenance approaches to PM. To support these implications, PM structure for successful parks regeneration does meet a holistic and multi-dimensional approach of place-keeping underlined by understanding policy contexts and rethinking current status quo of PM. Addressing these implications will shed light on urban PM in an era of austerity and ultimately contribute to improving people's well-being.