• Nuclear Engineering and Technology
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• 제39권3호
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• pp.215-220
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• 2007

The existing flooding Probabilistic Safety Analysis(PSA) was updated to reflect the Korean plant specific operating experience data into the flooding frequency to improve the PSA quality. Both the Nuclear Power Experience(NPE) database and the Korea Nuclear Pipe Failure Database(NuPIPE) databases were used in this study, and from these databases, only the Pressurized Water Reactor(PWR) data were used for the flooding frequencies of the flooding areas in the primary auxiliary building. With these databases and a Bayesian method, the flooding frequencies for the flooding areas were estimated. Subsequently, the Core Damage Frequency(CDF) for the flooding PSA of the Ulchin(UCN) unit 3 and 4 plants based on the Korean Standard Nuclear Power Plant(KSNP) internal full-power PSA model was recalculated. The evaluation results showed that sixteen flooding events are potentially significant according to the screening criterion, while there were two flooding events exceeding the screening criterion of the existing UCN 3 and 4 flooding PSA. The result was compared with two kinds of cases: (1) the flooding frequency and CDF from the method of the existing flooding PSA with the PWR and Boiled Water Reactor(BWR) data of the NPE database and the Maximum Likelihood Estimate(MLE) method and (2) the flooding frequency and CDF with the NPE database(PWR and BWR data), NuPIPE database, and a Bayesian method. From the comparison, a difference in CDF results was revealed more clearly between the CDF from this study and case (2) than between case (1) and case (2). That is, the number of flooding events exceeding the screen criterion further increased when only the PWR data were used for the primary auxiliary building than when the Korean specific data were used.

• 한국화재소방학회논문지
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• 제20권4호
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• pp.13-18
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• 2006

원자력발전소의 화재방호규정은 정성적인 화재위험성평가와 정량적인 화재위험도분석에 기반을 두며, 화재위험은 심층화재방어개념인 화재 예방, 화재 진압, 및 피해 최소화의 3가지 요소에 균형을 유지하면서 화재방호계획에 의해 관리되고 있다. 최근 화재위험 상세평가는 일반적으로 존모델 또는 필드모델을 이용하고 있다. 본 논문에서는 이런 추세에 따라 최신 화재모델링 도구인 FDS를 이용하여 원자력 발전소의 방화지역에 대한 정량적 화재위험분석 및 화재영향 평가가 가능한지 그 여부를 확인하였다. 이의 결과 화재모델링을 이용한 정량적 위험분석은 원자력발전소의 방화지역에 대한 정량적 위험도 분석뿐만 아니라 화재로 인한 원자로 노심 손상빈도를 개선할 수 있는 응용 도구로 활용될 수 있을 것으로 기대된다.

• 한국컴퓨터정보학회논문지
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• 제24권11호
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• pp.201-208
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• 2019

지능정보사회의 포노 사피엔스 시대에 대부분 기업 활동은 네트워크 및 정보시스템에 대한 의존도가 더욱 높아지고 있다. 우리나라 기업의 대부분을 차지하고 있는 중소기업은 보유하고 있는 정보 자산의 가치와 기술력이 점차 증가하고 있고 기업 성장의 원동력이 되는 핵심기술에 대한 보호역량은 기업의 가장 중요한 경쟁력이 될 것이다. 이에 따라 과학기술정보통신부와 한국인터넷진흥원은 높은 수준의 기업 맞춤형 정보보호 컨설팅 지원을 통해 중소기업의 현재 정보보호 수준을 평가하고 정보보호 역량을 제고함으로써 해킹, 정보유출 등 각종 사이버 위협으로부터 받는 피해를 최소화할 수 있는 기반을 제공하고 있다. 본 연구에서는 한국인터넷진흥원에서 수행한 중소기업 정보보호 컨설팅 결과를 기반으로 정보보호 효과를 분석하고 중소기업 정보보호 컨설팅 결과에서 도출된 문제점과 한계점을 파악하여 중소기업이 정보보호 관리체계를 보다 효율적이고 효과적으로 관리할 수 있는 중소기업 정보보호의 개선방안을 제안하도록 한다.

• 한국기계가공학회지
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• 제20권9호
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• pp.1-10
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• 2021

Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

• Structural Engineering and Mechanics
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• 제69권6호
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• pp.627-635
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• 2019

In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.

• Journal of Power Electronics
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• 제19권5호
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• pp.1303-1314
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• 2019

This paper studies the harmonic characteristics of ship electric propulsion systems and their treatment methods. It also adopts effective measures to suppress and prevent ship power systems from affecting ship operation due to the serious damage caused by harmonics. Firstly, the harmonic characteristics of a ship electric propulsion system are reviewed and discussed. Secondly, aiming at problems such as resonant frequency and filter characteristics variations, resonance point migration, and unstable filtering performances in conventional passive filters, a method for fully tuning of a passive dynamic tunable filter (PDTF) is proposed to realize harmonic suppression. Thirdly, to address the problems of the uncontrollable inductance L of traditional air gap iron core reactors and the harmonics of power electronic impedance converters (PEICs), this paper proposes an electromagnetic coupling reactor with impedance transformation and harmonic suppression characteristics (ECRITHS), with the internal filter (IF) designed to suppress the harmonics generated by PEICs. The ECRITHS is characterized by both harmonic suppression and impedance change. Fourthly, the ECRITHS is investigated. This investigation includes the harmonic suppression characteristics and impedance transformation characteristics of the ECRITHS at the fundamental frequency, which shows the good performance of the ECRITHS. Simulation and experimental evaluations of the PDTF are carried out. Multiple PDTFs can be configured to realize multi-order simultaneous dynamic filtering, and can effectively eliminate the current harmonics of ship electric propulsion systems. This is done to reduce the total harmonic distortion (THD) of the supply currents to well below the 5% limit imposed by the IEEE-519 standard. The PDTF also can eliminate harmonic currents in different geographic places by using a low voltage distribution system. Finally, a detailed discussion is presented, with challenges and future implications discussed. The research results are intended to effectively eliminate the harmonics of ship electric power propulsion systems and to improve the power quality of ship power systems. This is of theoretical and practical significance for improving the power quality and power savings of ship power systems.

• 한국재난정보학회 논문집
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• 제15권1호
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• pp.98-108
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• 2019

연구목적:본 연구는 화재 시 샌드위치패널 구조 창고의 벽 천장접합부 방호를 위한 스프링클러 성능확인 실험을 목적으로 한다. 연구방법: 현장조사결과를 기반으로 창고의 공간규격과 가연물을 선정하고 벽 코너 및 헤드 직하부에서의 방호실험을 수행하고 결과를 분석하였다. 연구결과:벽 코너 화재 시나리오에 대해서 K-80 폐쇄형 스프링클러헤드의 작동으로 샌드위치 패널의 착화 및 접합부 손상이 방지됨을 확인하였다. 결론:샌드위치패널 심재로의 착화 및 연소방지를 통한 화세제어로 이를 가정한 소방대의 소화 및 구조활동을 위한 표준진압대책이 마련되어야 한다.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3236-3246
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• 2021

Lessons learned from the Fukushima Daiichi nuclear power plant accident directed that multiple failures should be considered more seriously rather than single failure in the licensing bases and safety cases because attempts to take accident management measures could be unsuccessful under the high radiation environment aggravated by multiple failures, such as complete loss of electric power, uncontrollable loss of coolant inventory, failure of essential safety function recovery. In the case of the complete loss of electric power called station blackout (SBO), if there is no mitigation action for recovering safety functions, the reactor core would be overheated, and severe fuel damage could be anticipated due to the failure of the active heat sink. In such a transient condition at CANDU-6 plants, the seal failure of the primary heat transport (PHT) pumps can facilitate a consequent increase in the fuel sheath temperature and eventually lead to degradation of the fuel integrity. Therefore, it is necessary to specify the regulatory guidelines for multiple failures on a licensing basis so that licensees should prepare the accident management measures to prevent or mitigate accident conditions. In order to explore the efficiency of implementing accident management strategies for CANDU-6 plants, this study proposed a realistic accident analysis approach on the SBO transient with multiple-failure sequences such as seal failure of PHT pumps without operator's recovery actions. In this regard, a comparative study for two PHT pump seal failure modes with and without coolant seal leakage was conducted using a best-estimate code to precisely investigate the behaviors of thermal-hydraulic parameters during transient conditions. Moreover, a sensitivity analysis for different PHT pump seal leakage rates was also carried out to examine the effect of leakage rate on the system responses. This study is expected to provide the technical bases to the accident management strategy for unmitigated transient conditions with multiple failures.

• 한국콘텐츠학회논문지
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• 제21권2호
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• pp.587-593
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• 2021

본 논문에서는 나날이 발전하는 대규모 서비스거부공격에 대해 고전적인 방식의 DDoS 대응시스템에서 벗어나, 4차 혁명 시대의 핵심기술 중의 하나인 인공지능 기반의 기술을 활용해 지능화된 서비스거부공격을 효율적으로 감내 할 수 있는 서비스모델 개발방안을 제안하였다. 즉, 다수의 보안장비, 웹서버로부터 수집된 다량의 데이터를 대상으로 머신러닝 인공지능 학습을 통해 서비스거부공격을 탐지하고 피해를 최소화할 수 있는 방안을 제안하였다. 특히, 인공지능기술을 활용하기 위한 모델을 개발은 일정한 트래픽 변화를 반복하며 안정적 흐름의 데이터를 전송이 이루어지다가 서비스거부공격이 발생하면 다른 양상의 데이터 흐름을 보인다는 점에 착안하여 서비스서부공격 탐지에 인공지능기술을 활용하였다. 서비스거부공격이 발생하면 확률기반의 실제 트래픽과 예측값과의 편차가 발생하기 때문에 공격성 데이터로 판단하여 대응이 가능하다. 이 논문에서는 보안장비나 서버에서 발생하는 로그를 기반으로 데이터를 분석하여 서비스거부공격 탐지모델을 설명하였다.

• 대한건축학회논문집:계획계
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• 제33권12호
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• pp.105-112
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• 2017

Through various media, damage of both smoking and second-hand smoking has been recognized, and brought global scale of interest in antismoking. In Korea, government has tightened regulations of smoking in non-smoking zone since December, 1980, and after National Health Promotion Act in 1995, non-smoking zone has been gradually expanded. On the other hand, there were law suits to find those regulation towards smokers are either unconstitutional or not for 4 times. In this current state, people need smoking area to prevent second-hand smoking and to consider smokers in multi-unit dwelling. Main purpose of this research is to plan smoking spaces based on various typology of multi-dwelling plan for protection of both smokers and non-smokers' right. The research group collected and analyzed the smoking behaviors in various multi-unit dwelling types such as flat type, tower type, hybrid type and others. Based on those data, the group found three phenomena. First, there are internal regulations in multi-unit dwelling to make non-smoking zone based on National Health Promotion Act and resident representative meeting decision. Second, main smoking activities are occurring at major traffic line and entrances. Third, smoking inside of multi-unit dwelling complex causes second-hand smoking to residents live in $1^{st}$ floor and when they enter. Therefore, one can achieve both smokers' and non-smokers' protection of right by creating a designated smoking space near main entrances of multi-unit dwelling complex to consider smokers' and prevents second-hand smoking by using shaft space, which is in core space, to ventilate tobacco smoke through roof.