• Structural Engineering and Mechanics
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• v.25 no.4
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• pp.467-480
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• 2007

Two methods were developed for analyzing problems with two adjacent sub-domains modeled by different kinds of elements in finite element method. Each sub-domain can be defined independently without the consideration of equivalent division with common nodes used for the interface. These two methods employ an individual interface to accomplish the compatibility. The MLSA method uses the moving least square approximation which is the basic formulation for Element Free Galerkin Method to formulate the interface. The displacement field assumed by this method does not pass through nodes on the common boundary. Therefore, nodes can be chosen freely for this method. The results show that the MLSA method has better approximation than traditional methods.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.201-208
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• 2011

When designing a river, it is important to select the appropriate bank revetment methods, but there are no specific guidelines until now. Accordingly, it is important to prevent over-budgeting by deciding the suitability of the adopted bank revetment methods when designing a river. In this study, an assessment method was developed to assess the suitability of the adopted bank revetment methods when designing a river. By adopting this method to eight rivers, its validity was examined. Analytic Hierarchy Process (AHP) was used for the assessment, along with suitability index (SI) of the adopted bank revetment methods when designing a river. In order to select the best bank revetment methods, all environmental variables of the selected location have to be considered. Accordingly, to assess the designed bank revetment methods, all variables of the selected location have to be considered. The assessing items include hydraulic stability, environmental-ecological feasibility, economy, and amenity of the bank revetment. Each item includes four to five sub-items, and each sub-items reflect survey results on the locations. The assessment method was adopted and assessed for eight rivers, and bank revetments was designed to determine the SI. The result of this study is considered to be appropriate when assessing an eco-friendly bank revetment methods, and inappropriate designed bank revetments will guide future planners for selecting the most appropriate construction method.

• Journal of KIISE
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• v.43 no.5
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• pp.596-605
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• 2016

Since the Denial of Service Attack against multiple targets in the Korean network in private and public sectors in 2009, Korea has spent a great amount of its budget to build strong Internet infrastructure against DDoS attacks. As a result of the investments, many major governments and corporations installed dedicated DDoS defense systems. However, even organizations equipped with the product based defense system often showed incompetency in dealing with DDoS attacks with little variations from known attack types. In contrast, by following a capacity centric DDoS detection method, defense personnel can identify various types of DDoS attacks and abnormality of the system through checking availability of service resources, regardless of the types of specific attack techniques. Thus, the defense personnel can easily derive proper response methods according to the attacks. Deviating from the existing DDoS defense framework, this research study introduces a capacity centric DDoS detection methodology and provides methods to mitigate DDoS attacks by applying the methodology.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.2 s.13
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• pp.47-52
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• 2004

Whereas The masonry buildings are safe under gravity loads, most of the masonry buildings in Korea have many structural defects under a lateral load due to an earthquake acceleration. But there is no earthquake resistant design code for the Masonry in Korea. Therefore it may be necessary to be set up an seismic code and be suggested for reinforcing methods for existing masonry buildings. The purpose of this paper is to investigate seismic capacity of reinforced masonry buildings subjected to earthquake load. The typical two models of the masonry building in Korea are selected through a site investigation. On the basis of test results, the fiber reinforcing effect of the two models was considerable. The maximum base shear force and deformation capacity for RM were remarkably increased. It was found that the pier rocking failure was a dominant mode for the RM buildings during a seismic excitation.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.1-6
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• 2007

When the water content within concrete swells, diverse problems occur such as drop in durability. Due to this reason, a change is being managed in the unit water contents by using electric capacity measurements, high frequency heating methods, and unit-volume mass measurements, which are methods of measuring the unit water contents. Particularly, Japan is prescribing the guideline of management on a change in unit water content unit quantity $({\pm}10,\;15,\;20kg//m^3,\;etc.)$. However, the guideline of Japan dose not consider a fall in durability, and is decided on the value of pass-fail criteria by random fabrication errors and measurement errors. Consequently, this study was aimed to investigate the influence of a change In water content within concrete due to an addend caused by management error and to an artificial addend, upon drop in durability.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.143-151
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• 2009

Extreme hydrologic events cause serious disaster, such as flood and drought. Many researchers have an effort to estimate design rainfalls or discharges. This study evaluated parameter estimation methods to estimate probability rainfalls with low uncertainty which will be used in design rainfalls. This study collected rainfall data from Incheon, Gangnueng, Gwangju, Busan, and Chupungryong gage station, and generated synthetic rainfall data using ARMA model. This study employed the maximum likelihood method and the Bayesian inference method for estimating parameters of the Gumbel and GEV distribution. Using a bootstrap resampling method, this study estimated the confidence intervals of estimated probability rainfalls. Based on the comparison of the confidence intervals, this study recommended a proper parameter estimation method for estimating probability rainfalls which have a low uncertainty.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.119-125
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• 2003

Water flow in unsaturated soils is affected by two mathematical equations called soil water-characteristic curve and permeability-suction relationship. Soil water-characteristic curve is an equation showing volumetric water content-suction relationship. Many researchers have presented equations for the relationships. This paper illustrates the importance of correctly determining the two relationships when analyzing unsaturated water flows. Results from two methods, Gardner (1958) and Fredlund et al. (1994), are used for comparison purposes. Numerical simulations of water flow by finite element method are performed using the two methods. The results by the numerical simulations are compared with the field data which was obtained from time-domain reflectometry (TDR) probes in Delaware County, Ohio. This data was obtained by the Seasonal Instrumentation Program which is included as a part of the Strategic Highway Research Program (SHRP).

• Journal of Environmental Policy
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• v.8 no.4
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• pp.171-198
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• 2009

The issue of burden sharing between sectors has become a pertinent national issue with respect tothe establishment of national greenhouse gas (GHG) reduction targets, and the means to achieve these targets. This study explores methods for equitable sectoral allocation to reduce GHGs based on an allocation index taking into account relevant attributes in line with national GHG emissions trends and structures. This paper considered potential for GHG reduction, rate of increase of emissions, and ability to pay as suitable criteria for analysis of each sector. As a result of the analysis, it was found that equitable allocation methods have significantly different burden sharing compared to allocation that considers only potential for GHG reduction. Accordingly, further empirical study on various simulations based on national economic impact will be essential for better policy solutions. This study will contribute to applying national allocation plans in a logical, consistent and transparent manner.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.63-69
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• 2008

It has an important meaning that the maintenance and management of facility for a onshore construction shall be damaged by oceanic environment. A movement and displacement of these shall be investigated by up-to-date machinery tools like GPS and Lidar and MBES & Gyro. In current a lot of tools and methods for investigation shall be used as a displacement and movement on land mainly. For underwater facility it is very difficult to check because of special conditions below the water surface. In this study, a surveying methods for a movement and displacement of underwater facility as caisson shall be used, i.e. multibeam-echo-sounding system. A possibility as basic data for displacement and environmental monitoring shall be studied by MBES to acquire a caisson's inclination.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.123-133
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• 2009

In this study, we developed the GIS-based Geomorpho-hydrological Watershed Modeling System($G^{2}WMS$) which could consider both nonlilear rainfall-runoff relationship based on Geomorpho-Climatic Unit Hydrograph(GCUH) as well as watershed system inducing river routing. The developed new model was calibrated at the gaged rainfall events at natural watersheds and previewed to apply at the ungaged mountain basins, such as Sulma basin for small mountain basin and Andong-Dam basin for large scale basin, compared single with partitioned basin in the observed unit hydrographs and rainfall-discharge events. Finally, at the large scale Andong dam basin, we concluded that partitioned basin cases which including th nonlinear GCUH and river routing methods were superior to single basins which including the traditional methods in rainfall-discharge simulation at the mountain basins.