• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.445-454
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• 2008

Many countermeasures for local scour at bridge piers constructed on the river and sea have been developed and researched to protect piers against local scour. The most commonly employed method is riprap protection, which is sometimes required the filter installation between riprap and base layers. However, the construction of stone filters are really hard to perform in the field, require the high cost, or sometimes are impossible. The experimental modeling is conducted to analyze the riprap failure modes and the stability of riprap protection without filters based on the different approach velocity and riprap layer thickness conditions. Also, the stability index to evaluate the performance of riprap protection is developed using the experimental results. The cover and thickness of the riprap layer play a very important role in the stability and thicker riprap layers can prevent a total disintegration of the riprap layer effectively, especially due to winnowing failure.

• Journal of Korean Society of Transportation
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• v.36 no.1
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• pp.51-65
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• 2018

Intentional aggressive driving (IAD) is defined as a hazardous driving event that the aggressive driver intentionally threatens neighbor drivers with abrupt longitudinal and lateral maneuvering. This study developed a methodology for detecting IAD events based on the analysis of interactions between aggressive driver and normal driver. Three major aggressive events including rear-close following, side-close driving, and sudden deceleration were analyzed to develop the algorithm. Then, driving simulation experiments were conducted using a multi-agent driving simulator to obtain data to be used for the development of the detection algorithm. In order to detect the driver's intention to attack, a relative evaluation index (Erratic Driving Index, EDI) reflecting the driving pattern was derived. The derived IAD event detection algorithm utilizes both the existing absolute detection method and the relative detection method. It is expected that the proposed methodology can be effectively used for detecting IAD events in support of in-vehicle data recorder technology in practice.

• Journal of Navigation and Port Research
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• v.32 no.6
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• pp.439-445
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• 2008

Various turning tests were carried out according to the rudder angle, turning direction, and the speed etc. with the ship's maneuverability measuring system on the training ship HANBADA. After that they were compared with each other on the turning circle, maneuvering performance index and the distance of new course, and then found out that they were satisfied with the IMO maneuvering standards. And the turning circles of port were smaller than those of starboard with all the rudder angles and maneuvering indexes such as K and T were relatively bigger than other vessels. Also, the distance cf new course was measured to $125{\sim}300m$ in case of the new course on $30^{\circ}{\sim}90^{\circ}$. All of these results will be helpful to escape from collision and to alter course on coastal voyage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.149-156
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• 2017

Nuclear fuel requires high reliability and safety and therefore contains debris filtering devices to prevent failure-inducing debris from entering it. The debris filtering performance of nuclear fuel is one of the most important factors for fuel integrity. Therefore, the performance must be evaluated and the measurement must be reasonable. In this study, a calculation method of the comprehensive filtering efficiency using the weighted mean was proposed to establish a standard filtering efficiency index. To confirm the suitability of the proposed method, representative debris specimens were selected and the filtering efficiency with the weighted mean was compared with the efficiency of the arithmetic mean. The weighting factor of the weighted mean was introduced to produce a fair evaluation. In addition, the analysis of the debris filtering mechanism was performed according to the size of debris specimens, and the main dimensions of the filtering feature for commercial nuclear fuel.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.29-40
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• 2019

Mechanized constructions have been frequently increased in soft ground below sea bed or river bed, for urban tunnel construction, and for underpinning the lower part of major structures in order to construct a safer tunnel considering various risk factors during the tunnel construction. However, it is difficult to estimate the subsidence behavior of the ground surface due to excavation and needs to be easily predicted. Thus, in this study, when a twin tunnel is constructed in the soft ground, it is proposed a simpler equation relating to the settlement behavior and a corrected formula applicable to soft ground and large diameter shield tunnels based on the previously proposed theory by Peck (1969). For this purpose, it was analyzed to long-term measurement values such as the amount of maximum settlement, the subsidence range by ground conditions, and interference volume loss due to the parallel construction, etc. As a result, a equation was suggested to predict the amount of maximum settlement in the soft sediment clay ground where is located at the upper part of the excavation site. It is turned out that the proposed equation is more suitable for measurement data in Korea than Peck (1969)'s.

• The Journal of the Convergence on Culture Technology
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• v.7 no.3
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• pp.383-395
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• 2021

The diversity of urban landscapes is established by dynamic characteristics such as language, color, and their movement, which are the building environment, street patterns, and people. With the increase of foreign migrants in Korea, new guidelines are needed in terms of local community administration and land policy. Administrative, sociological, and geographical studies have been conducted on the steadily increasing number of foreign migrants since the 2000s, but it is difficult to establish for making safe and healthy communities through which different cultures and lifestyles of each country and ethnic group undergo some integration with the existing host society. There are limitations in identifying the lack of statistical data and the representation of a minority proportion of foreign residents. In order to analyze the core elements of the integrated strategy of the local community, the residential behavior and spatial characteristics of foreign migrants must first be identified.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.449-449
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• 2023

유량은 도섭법, 보트법, 횡측선법, 교량법 및 부자법 등 다양한 방법으로 측정되는데, 이들 측정방법 모두 많은 수의 관측자를 필요로 한다. 이들은 하천에 직접 들어가서 측정하거나, 인공구조물인 교량과 재방에서 측정되는데, 도섭법, 보트법, 횡측선법이 전자이며, 고수위 및 고유속으로 하천에 들어가지 못하는 경우에는 교량법 및 부자법을 사용하여 유량을 측정한다. 최근 지구 온난화로 따른 이상 기후가 빈번히 발생하고 있으며, 이로 인한 많은 피해가 발생하고 있어, 하천 수위, 유속 모니터링에 대한 중요성이 더 커지고 있다. 2022년 1월부터 시행 중인 「중대재해처벌법」으로 집중호우 및 일몰 이후에는 안전상의 문제로 유량측정이 어려운 상황으로 필요한 시기에 유량 데이터를 확보에 제약이 있다. 이에 관측자 없이도 유량을 측정할 수 있는 방법을 이용하여 중대 재해의 위험성을 해소하고자 하였다. 유량측정 방법으로 설치 회수가 용이한 비접촉 방식에서 영상표면유속측정 방식과 레이더(전자파)표면 유속측정 방식 중, 집중호우 및 태풍 발생 중 가시성이 확보되지 않아도 측정이 가능한 레이더(전자파) 표면유속계를 이용한 다측점 유량측정 방법을 개발하였다. 비접촉 다측점 유량측정시스템 Master 1대에 8대의 Slave를 연결할 수 있어 총 9개의 측선을 측정할 수 있게 개발하였다. 특히, 하천 및 수로 등의 표면 유속을 비접촉으로 측정하고 하천 단면을 이용하여 유량측정이 가능한 장비로 별도의 수중 및 수상 주조물 작업이 필요 없고 장비의 손상 및 유실 가능성이 거의 없고 역류 상태에서도 측정이 가능하다. 유속은 24GHz의 레이더 주파수를 송수신하여 도플러 변이를 이용하여 측정하였고, 수위는 80GHz의 레이더 주파수를 사용하여 왕복 시간을 거리로 환산하여 측정하였다. 유량은 각각의 유속계에 단면을 입력해 놓으면 유속분포법, 중간단면적법 및 지표유속법을 적용하여, 각각의 측선에 대한유량과 총 유량을 산출하였다. 그 결과, 기존 방식 대비 상당한 개선 효과를 확인하였고, 향후 환경부 등 중앙부처의 수문조사 사업에서 그 역할이 기대된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3A
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• pp.209-216
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• 2009

The structural stability as well as economical efficiency of the wind sensitive structures are strongly dependant on accurate evaluation of the design wind speed. Present study demonstrates a useful wind data obtained at the wind monitoring tower in the Kwangyang Suspension Bridge site. Moreover the Measure-Correlate-Predict (MCP) method has been applied to estimate the long-term wind data at the bridge site based on the wind data at the local weather station. The measured data indicate that the turbulent intensities and roughness exponents are strongly affected by the wind direction and surrounding topography. The new design wind speed based on MCP method is 20m/s lower than that at the original estimation, and the resulting design wind load is only 36% of the old prediction. The field measurement of wind data is recommended to ensure the economical and secure design of the wind sensitive structures because the measured wind data reveal much different from the estimated one due to local topography.

• Journal of the Korean Regional Science Association
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• v.37 no.4
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• pp.33-47
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• 2021

In urban declining areas, the population is decreasing, and drying environments such as buildings and facilities are aging. Therefore, it is vulnerable in the event of disaster, and recovery takes a lot of time and money. The purpose of this study is to develop an evaluation technique for comprehensively diagnosing disasters in declining areas and to present implications through case analysis. Evaluation indicators were selected to calculate the comprehensive diagnosis index of disasters, and weights were calculated for each class, including disaster types, components, and evaluation indicators, through Analytic Hierarchy Process analysis. The comprehensive diagnoses index for each type of disaster was calculated with the calculated weight, and the risk according to the level of urban decline was analyzed. As a result of analyzing Seoul as a case area, it was analyzed that the overall risk of disasters was high in southern regions such as Seocho-gu, Dongjak-gu, Geumcheon-gu, and Gangseo-gu, and relatively low in downtown and northern Seoul, parks and green areas. The results of this study are of academic significance in that they presented a comprehensive diagnostic index evaluation system and technique for each type of disaster, including natural and social disasters.

• Journal of Korea Water Resources Association
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• v.52 no.3
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• pp.187-194
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• 2019

Intake ratio from river constitutes about 31% (8/26) that beings to "water stress country" as "Medium ~ High" with China, India, Italy, South Africa, etc. Therefore, the present study on a dam that is the most effective and direct for securing water resources has been performed. First of all, climate change scenarios were investigated and analyzed. RCP 4.5 and 8.5 with 12.5 km grid resolution presented in the IPCC (Intergovernmental Panel on Climate Change) 5th Assessment Report (AR5) were applied to study watershed using SWAT (Soil and Water Assessment Tool) and HEC-ResSim models that carried out co-operation. Based on the results of dam simulation, the reduction effects of floods and droughts were quantitatively presented. The procedures of dam projects of the USA, Japan and Korea were investigated. As a result, there are no estimating quantitative criteria, calculating methods or formulas. In the present study, therefore, indexes for selecting suitable dam site through literature investigation and analyzing dam watersheds were determined, Expert questionnaire for various indexes were performed. Based on the above mentioned investigation and expert questionnaire, a methodology assigning weight using AHP method were proposed. The function of suitable dam (FSDS) site was calibrated and verified for four medium-sized watersheds. Finally, automated model for suitable dam site was developed using FSDS and 'Model builder' of GIS tool.