• Journal of Wetlands Research
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• v.21 no.2
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• pp.132-139
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• 2019

Bi-directional interaction between vegetation and groundwater table has a great influence on the dynamics of wetland vegetation. In this study, nonlinear dynamics of wetland vegetation affected by groundwater are analyzed. The effect on groundwater is described as a loss term in the governing equation of wetland vegetation and it is explored how the wetland vegetation is likely to converge into two attractors by groundwater table change. From this conceptual approach, the vulnerability to catastrophic shifts in stable state where the current vegetation species are extinct and stabilized by other vegetation species is analyzed in response to groundwater table.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.2
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• pp.117-131
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• 2006

A coupled T-H-M(Thermo-Hydro-Mechanical) analysis was carried out for KENTEX (KAERI Engineering-scale T-H-M Experiment for Engineered Barrier System), which is a facility for validating the coupled T-H-M behavior in the engineered barrier system of the Korean reference HLW(high-level waste) disposal system. The changes of temperature, water saturation, and stress were estimated based on the coupled T-H-M analysis, and the influence of the types of mechanical constitutive material laws was investigated by using elastic model, poroelastic model, and poroelastic-plastic model. The analysis was done using ABAQUS, which is a commercial finite element code for general purposes. From the analysis, it was observed that the temperature in the bentonite increased sharply for a couple of days after heating the heater and then slowly increased to a constant value. The temperatures at all locations were nearly at a steady state after about 37.5 days. In the steady state, the temperature was maintained at $90^{\circ}C$ at the interface between the heater and the bentonite and at about $70^{\circ}C$ at the interface between the bentonite and the confining cylinder. The variation of the water saturation with time in bentonite was almost same independent of the material laws used in the coupled T-H-M processes. By comparing the saturation change of T-H-M and that of H-M(Hydro-Mechanical) processes using elastic and poroelastic material mod31 respectively, it was found that the degree of saturation near the heater from T-H-M calculation was higher than that from the coupled H-M calculation mainly because of the thermal flux, which seemed to speed up the saturation. The stresses in three cases with different material laws were increased with time. By comparing the stress change in H-M calculation using poroelasetic and poroelasetic-plastic model, it was possible to conclude that the influence of saturation on the stress change is higher than the influence of temperature. It is, therefore, recommended to use a material law, which can model the elastic-plastic behavior of buffer, since the coupled T-H-M processes in buffer is affected by the variation of void ratio, thermal expansion, as well as swelling pressure.

• Journal of the Korean Geographical Society
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• v.47 no.5
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• pp.677-699
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• 2012

Climate changes may cause substantial changes in spatial patterns and distribution of vector-borne diseases (VBD's), which will result in a significant threat to humans and emerge as an important public health problem that the international society needs to solve. As global warming becomes widespread and the Korean peninsula characterizes subtropical climate, the potentials of climate-driven disease outbreaks and spread rapidly increase with changes in land use, population distributions, and ecological environments. Vector-borne diseases are typically infected by insects such as mosquitoes and ticks, and infected hosts and vectors increased dramatically as the habitat ranges of the VBD agents have been expanded for the past 20 years. Medical geography integrates and processes a wide range of public health data and indicators at both local and regional levels, and ultimately helps researchers identify spatiotemporal mechanism of the diseases determining interactions and relationships between spatial and non-spatial data. Spatial epidemiology is a new and emerging area of medical geography integrating geospatial sciences, environmental sciences, and epidemiology to further uncover human health-environment relationships. An introduction of GIS-based disease monitoring system to the public health surveillance system is among the important future research agenda that medical geography can significantly contribute to. Particularly, real-time monitoring methods, early-warning systems, and spatial forecasting of VBD factors will be key research fields to understand the dynamics of VBD's.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.175-186
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• 2023

The buffer materials in disposal hole are exposed to the decay heat from spent nuclear fuels and groundwater inflow through adjacent rockmass. Since understanding of thermal-hydro-mechanical-chemical (T-H-M-C) interaction in buffer material is crucial for predicting their long-term performance and safety of disposal repository, it is necessary to investigate the heating-hydration characteristics and consequent T-H-M-C behavior of the buffer materials under disposal conditions considering geochemical factors. In response, the Korea Atomic Energy Research Institute developed a laboratory-scale 'Lab.THMC' experiment system, which characterizes the T-H-M behavior of buffer materials under different geochemical conditions by analyzing heating-hydration process and stress changes. This technical report introduces the detail design of the Lab.THMC system, summarizes preliminary experimental results, and outlines future research plans.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.46-49
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• 2001

EMV(electromagnetic valve) 시스템은 자동차에서 기계식 캠을 사용하지 않고 전자기력을 이용하여 흡 배기 밸브를 작동시키고 타이밍을 조절하기 위한 것이다. 본 논문에서는 EMV 시스템을 위한 전자기와 기계적 모델을 사용하여 그에 대한 동역학 모델을 유도하였다. EMV 시스템의 최대 동작주파수가 가솔린엔진의 최대 회전수 6000rpm에 대응한 valve의 주파수가 50Hz 되기 위한 제어기를 설계하였고, 실험을 통하여 문제점들을 파악하고자 한다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2010.05a
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• pp.197-198
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.83-84
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• 2009

• Bulletin of the Korean Space Science Society
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• 2007.04a
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• pp.81-81
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• 2007

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2012.05a
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• pp.279-280
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• 2012

• Proceedings of the Korean Institute of Landscape Architecture Conference
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• 2022.10a
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• pp.106-107
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• 2022