• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.167-180
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• 2022

A strategic structure when exposed to direct hit of conventional bomb/projectile are severely damaged because of large amounts of energy released by the impact and penetration of bomb. When massive concrete slabs suffer a direct hit, the energy released during impact and penetration process are able to easily break up large mass of concrete. When over stressed under such impact of bombs, the concrete structure fails showing brittle behavioural nature. This paper is intended to study and suggest the protective measures for structures used for strategic application by adopting a means to dissipate the large quantum of energy released. To quantitatively evaluate the force, displacement and energy in such scenario, a fine numerical model of the proposed layered structure of different combinations was built in ANSYS programme in which tri-nitrotoluene (TNT) explosive was detonated at penetration depth calculated for GP1000 Lbs bomb. The distinct blast mitigation effect of the proposed structure was demonstrated by adopting various layers/barriers created as protective measures for the strategic structure. The calculated result shows that the blast effect on the structure is potentially reduced due to provision of buster slab with sand cushioning provided as protective measure to the main structure. This concept of layered protective measures may be adopted for safeguarding strategic structures such as Domes, Tunnels and Underground Structures.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.443-453
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• 2011

This research aims at suggesting the mitigation measures of decreasing pollution by analyzing land cover characteristics according to subwatershed, and non-pollutant load characteristics occurring in each subwatershed. Mushim-cheon is selected as a research area, and HyGIS-SWAT is used as a water quality model. This research analyzed outflow load characteristics by classifying land cover, which has over 50% classified items, into a city area, a farmland area and a forest area. The result shows that the yearly occurrence load quantity represents a farmland area, a forest area and a city area in order. In subwatershed-2, occurrence load quantity is analyzed by setting up a buffer zone in the center of stream, and by changing a farmland area into a natural grass land. Therefore, a farmland area in a subwatershed changes 36.6% into 27.9% and 15.3% comparing to previous land cover change. In the analysis of sediment loads occurrence quantity and nutritive salt load occurrence quantity in subwatershed-2, sediment loads occurrence quantity decreases 52% to about 47%, and nutritive salt load decreases 49% and 34% in compare with previous change. Hereafter, this research will set up the mitigation measures scenario, and find out which is more effective for the mitigation measures.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.462-472
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• 2017

Sunken vessels on major fairways can cause many problems in terms of maritime safety and the marine environment. In order to prevent secondary marine pollution accidents caused by sunken vessels, information on sunken vessels has been collected, a risk assessment has been conducted, and the relevant vessels are being managed according to the results of each assessment. However, there is still a demand for improvements. The most important of the improvement plans is a paradigm shift. In other words, the management of sunken vessels needs to be transformed according to a new paradigm to manage all sunken vessels within three years from the time of sinking. Legislative improvements are also needed for the reporting system for sunken vessels, risk assessment tools, the implementation of risk mitigation measures, and criteria for the implementation cost of risk mitigation measures. In addition, close coordination between marine pollution response and sunken vessel management efforts is needed. As the division of duties between the Korea Coast Guard and the Ministry of Oceans and Fisheries is vague, collaboration between the two ministries is required. Close collaboration is also needed between the departments of navigation safety management and sunken vessel management. Therefore, it is necessary to more clearly establish the relationship between the two systems and create a synergy effect between the two administrative operations using the results of the risk assessment in the Marine Environment Management Act to determine the navigational risk posed by obstacles with regard to the Maritime Safety Act.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.139-150
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• 2019

Though, fishing vessel accidents account for 70 % of all maritime accidents in Korean waters, most research has focused on identifying causes and developing mitigation policies in an attempt to reduce this rate. However, predicting and evaluating accident risk needs to be done before the implementation of such reduction measures. For this reasons, we havve performed a risk analysis to calculate the risk of accidents and propose a risk criteria matrix with 4 quadrants, within one of which forecasted risk is plotted for the relative comparison of risks. For this research, we considered 9 types of fishing vessel accidents as reported by Korea Maritime Safety Tribunal (KMST). Given that no risk evaluation criteria have been established in Korea, we established a two-dimensional frequency-consequence grid consisting of four quadrants into which paired frequency and consequence for each type of accident are presented. With the simple structure of the evaluation model, one can easily verify the effect of frequency and consequence on the resulting risk within each quadrant. Consequently, these risk evaluation results will help a decision maker employ more realistic risk mitigation measures for accident types situated in different quadrants. As an application of the risk evaluation matrix, accident types were further analyzed using accident causes including human error (factor) and appropriate risk reduction options may be established by comparing the relative frequency and consequence of each accident cause.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.1
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• pp.59-67
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• 2015

Because reservoirs that supply irrigation water play an important role in water resource management, it is necessary to evaluate the vulnerability of this particular water supply resource. The purpose of this study is to provide water supply risk maps of agricultural reservoirs in South Korea using irrigation vulnerability model and cluster analysis. To quantify water supply risk, irrigation vulnerability indices are estimated to evaluate the performance of the water supply on the agricultural reservoir system using a probability theory and reliability analysis. First, the irrigation vulnerability probabilities of 1,346 reservoirs managed by Korea Rural Community Corporation (KRC) were analyzed using meteorological data on 54 meteorological stations over the past 30 years (1981-2010). Second, using the K-mean method of non-hierarchical cluster analysis and pre-simulation approach, cluster analysis was applied to classify into three groups for characterizing irrigation vulnerability in reservoirs. The morphology index, watershed area, irrigated area, and ratio between watershed and irrigated area are selected as the clustering analysis parameters. It is suggested that the water supply risk map be utilized as a basis for the establishment of risk management measures, and could provide effective information for a reasonable decision making on drought risk mitigation.

• Structural Engineering and Mechanics
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• v.70 no.6
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• pp.765-779
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• 2019

Most of the existing evaluation criteria of vibration serviceability rely on the peak acceleration of the structure rather than that of the people keeping their own body unmoved on the structure who is the real receiver of structural vibrations. In order to accurately assess the vibration serviceability, therefore, a full path assessment approach of vibration serviceability based on vibration source, path and receiver is not only tentatively proposed in this paper, taking the peak acceleration of receiver into account, but also introduce a probability procedure to provide more instructive information instead of a single value. In fact, semi-rigid supported on both sides of the structure is more consistent with the actual situation than simply supported or clamped due to the application of the prefabricated footbridge structures. So, the footbridge is regarded as a beam with semi-rigid supported on both sides in this paper. The differential quadrature-integral quadrature coupled method is not only to handle different type of boundary conditions, but also after being further modified via the introduction of an approximation procedure in this work, the time-varying system problem caused by human-structure interaction can be solved well. The analytical results of numerical simulations demonstrate that the modified differential quadrature-integral quadrature coupled method has higher reliability and accuracy compared with the mode superposition method. What's more, both of the two different passive control measures, the tuned mass damper and semi-rigid supported, have good performance for reducing vibrations. Most importantly, semi-rigid supported is easier to achieve the objective of reducing vibration compared with tuned mass damper in design stage of structure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.3
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• pp.916-937
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• 2023

Most of the existing Distributed Denial-of-Service mitigation schemes in Software-Defined Networking are only implemented in the network domain managed by a single controller. In fact, the zombies for attackers to launch large-scale DDoS attacks are actually not in the same network domain. Therefore, abnormal traffic of DDoS attack will affect multiple paths and network domains. A single defense method is difficult to deal with large-scale DDoS attacks. The cooperative defense of multiple domains becomes an important means to effectively solve cross-domain DDoS attacks. We propose an efficient multi-domain DDoS cooperative defense mechanism by integrating blockchain and SDN architecture. It includes attack traceability, inter-domain information sharing and attack mitigation. In order to reduce the length of the marking path and shorten the traceability time, we propose an AS-level packet traceability method called ASPM. We propose an information sharing method across multiple domains based on blockchain and smart contract. It effectively solves the impact of DDoS illegal traffic on multiple domains. According to the traceability results, we designed a DDoS attack mitigation method by replacing the ACL list with the IP address black/gray list. The experimental results show that our ASPM traceability method requires less data packets, high traceability precision and low overhead. And blockchain-based inter-domain sharing scheme has low cost, high scalability and high security. Attack mitigation measures can prevent illegal data flow in a timely and efficient manner.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.257-266
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• 2021

Urban areas can often suffer flood damage because of the more frequent catastrophic rainfall events from climate change. Flood mitigation measures consist of (1) structural and (2) non-structural measures. In this study, the proposed method focused on operating an urban drainage system among non-structural measures. The combined inland-river operation technique estimates the inflow of pump stations based on the water level obtained from a preselected monitoring point, and the pump station expels the stored rainwater to the riverside based on those estimates. In this study, the proposed method was applied to the Mokgam drainage watershed, where catastrophic rainfall events occurred (i.e., 2010- and 2011-years), and severe flood damage was recorded in Seoul. Using the proposed method, the efficiency of flood reduction from the two rainfall events was reduced by 34.9 % and 54.4 %, respectively, compared to the current operation method. Thus, the proposed method can minimize the flood damage in the Mokgam drainage watershed by reserving the additional storage space of a reservoir. In addition, flooding from catastrophic rainfall can be prevented, and citizens' lives and property in urban areas can be protected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.478-480
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• 2014

In this paper, Evaluate the effects of the lower layer of sensitive facilities against vibration and noise cinemas at the time of installation to the leisure facilities of the building of new and proposed mitigation measures for them.

• International Journal of High-Rise Buildings
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• v.7 no.1
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• pp.85-93
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• 2018

The design of a supertall building poses many challenges to the architect and engineer. Using Jeddah Tower as a case study; this paper intends to discuss a few of those challenges specifically related to the arrangement of programmed spaces in the tower, their functional connection by means of the vertical transportation system and physical connection with shafts which introduces the potential for stack effect in the building. The measures applied in response to and mitigation of these issues are discussed.