• Journal of Communications and Networks
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• 제16권5호
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• pp.534-547
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• 2014

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

• 한국안전학회지
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• 제31권5호
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• pp.95-101
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• 2016

This study proposes a multi-scale dynamic system reliability analysis of control system as a method of quantitative evaluation of its performance in probabilistic terms. In this second paper, we discuss the control effect of the viscous damper on the seismic performance of the structure-level failure. Since the failure of one structural member does not necessarily cause the collapse of the structural system, we need to consider a set of failure scenarios of the structural system and compute the sum of the failure probabilities of the failure scenarios where the statistical dependence between the failure scenarios should be taken into account. Therefore, this computation requires additional system reliability analysis. As a result, the proposed approach takes a hierarchial framework where the failure probability of a structural member is computed using a lower-scale system reliability with the union set of time-sequential member failures and their statistical dependence, and the failure probability of the structural system is again computed using a higher-scale system reliability with the member failure probabilities obtained by the lower-scale system reliability and their statistical dependence. Numerical results demonstrate that the proposed approach can provide an accurate and stable reliability assessment of the control performance of the viscous damper system on the system failure. Also, the parametric study of damper capacity on the seismic performance has been performed to demonstrate the applicability of the proposed approach through the probabilistic assessment of the seismic performance improvement of the damper system.

• 한국환경과학회지
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• 제17권11호
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• pp.1295-1305
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• 2008

This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

• 한국환경과학회지
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• 제17권11호
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• pp.1281-1293
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• 2008

This study aims at the estimation of dam failure time and dam failure scenario analysis of and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-HMS, DAMBRK-FLDWAV simulation model. As the result of the rainfall-runoff simulation, the lancet flood amount of the Yeoncheon Dam site was $10,324\;m^3/sec$ and the total outflow was $1,263.90\;million\;m^3$. For the dam failure time estimation, 13 scenarios were assumed including dam failure duration time and starting time, which reviewed to the runoff results. The simulation time was established with 30 minutes intervals between one o'clock to 4 o'clock in the morning on August 1, 1999 for the setup standard for each case of the dam failure time estimation, considering the arrival time of the flood, when the actually measured water level was sharply raising at Jeongok station area of the Yeoncheon Dam downstream, As results, dam failure arrival time could be estimated at 02:45 a.m., August 1st 1999 and duration time could be also 30 minutes. Those results and procedure could suggest how and when dam failure occurs and analyzes.

• 한국가스학회지
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• 제11권4호
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• pp.98-103
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• 2007

발생가능성 분석은 염소공정의 염소투입설비에서 누출 가능성을 교정하는데 자주 사용되고 있다. 그리고 이러한 시설은 전형적으로 압력용기, 기화기, 배관, 측량장비, 안전장치로 등으로 구성되어 있다. 이 논문에서는 가능성 분석절차와 기계적 요소들의 고장률에 대하여 사건 시나리오를 만들 인적오류도 고려하였다. 논문의 주된 목적은 결정된 각각의 시나리오의 발생가능성을 계산하는 것으로 발생가능성분석 방법에 근거하여 기계요소의 고장률과 인적오류를 포함하여 계산하였다. 그 결과, 주요 $Cl_2$ 취급공정에서 누출이 발생할 가능성이 $5.73{\times}10^{-5}$로 예측되었으며 세정시스템의 고장확률은 $4.11{\times}10^{-2}$로 나타났다.

• Structural Engineering and Mechanics
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• 제54권6호
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• pp.1111-1133
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• 2015

Rebar corrosion in concrete is one of the main causes of reduction of service life of reinforced concrete buildings. This paper presents the influence of rebar corrosion on the structural behavior of reinforced concrete (RC) buildings subjected to strong earthquake ground motion. Different levels of rebar corrosion scenarios were applied on a typical four story RC frame. The deteriorated conditions as a result of these scenarios include loss in cross-sectional area and loss of mechanical properties of the reinforcement bars, loss in bond strength, and loss in concrete strength and its modulus of elasticity. Dynamic analyses of the frame with different corrosion scenarios are performed with selected strong earthquake ground motion records. The influences of degradation in both concrete and reinforcement on structural behavior are investigated by comparing the various parameters of the frame under different corrosion scenarios with respect to each other. The results show that the progressive deterioration of the frame due to rebar corrosion causes serious structural behavior changes such as change in failure mode. The intensity, propagation time, and extensity of rebar corrosion have very important effects on the level of degradation of steel and concrete, as well as on the earthquake behavior of the structure.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.161-162
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• 2018

• 한국가스학회:학술대회논문집
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• 한국가스학회 2007년도 춘계학술발표회 논문집
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• pp.180-185
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• 2007

Likelihood analysis was used for the revision of release probability/frequency in chlorine Injection facilities used in chlorine process. Typically these facilities consist of pressure cylinder, vaporizer, pipeline, measuring equipment and safety equipment. This paper described the incident scenarios considered, likelihood analysis procedure and the selection and application of basic events and for failure rates of mechanical components. Human errors were also considered. The major objective of this paper is to estimate the likelihood of each determined incident scenarios. We estimated failure rates of mechanical components based on likelihood analysis procedure. Human errors were also considered. It was estimated to have $5.73{\times}10^{-5}\;Cl_2$ leak per year during the major $Cl_2$ handling process. The probability of failure in scrubber system was $4.11{\times}10^{-2}/demand$.

• 한국ITS학회 논문지
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• 제22권6호
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• pp.264-283
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• 2023

자율주행차량 사고는 일반차량 사고와 다르게 기술적 문제, 환경, 운전자와의 상호작용 등 다양한 요인에 기인한 사고 발생 가능성이 존재한다. 향후 자율주행 기술의 진보로 기존의 사고원인 이외에도 새로운 이슈들이 대두될 것으로 예상되며, 이에 대응하기 위한 다양한 시나리오 기반의 접근법이 필요하다. 본 연구에서는 자율주행 사고 리포트인, CA DMV collision report와 자율주행모드 해제 보고서인 Disengagement report, 자율주행 실제 사고영상을 수집하여 자율주행차량 교통사고 시나리오를 개발하였다. 시나리오는 ISO 26262의 기능안전 시스템 failure mode에 기반하여 도출되었으며, 자율주행 기능의 다양한 이슈를 반영하고자 하였다. 본 연구를 통해 도출된 자율주행차량 시나리오는 향후 다양한 자율주행차량 교통사고 예방과 대비에 기여할 뿐만 아니라 자율주행 기술의 안전성을 향상시키는 데 중요한 역할을 할 것으로 기대한다.

• Structural Engineering and Mechanics
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• 제81권1호
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• pp.59-68
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• 2022

Prestressed prefabricated hollow core concrete slabs with spans of 5 m and 10 m are commonly used since last century and still in service due to the advantage of construction convenience and durability. However, the end slabs are regularly subjected to cracks at the top and fail with brittleness due to the asymmetric boundary conditions. To better maintain such widely used type of hollow core slabs, the effect of asymmetric constraint in the end slabs are systematically studied through detailed nonlinear finite element analyses and experimental data. Experimental tests of slabs with four prestressed tendons and seven prestressed tendons with different boundary conditions were conducted. Results observe three failure modes of the slabs: the bending failure mode, shear and torsion failure mode, and transverse failure mode. Detailed nonlinear finite element models are developed to well match the failure modes and to reveal potential damage scenarios with asymmetric boundary conditions. Recommendations regarding ultimate capacity of the slabs with asymmetric boundary conditions are made to ensure a safe and rational design of prestressed concrete hollow slabs for short span bridges.