• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.356.1-356
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• 1999

• Journal of Korean Society on Water Environment
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• v.27 no.2
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• pp.218-227
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• 2011

The objective approach for assessment of stream naturalness is an essential part of the stream restoration project. This study proposes the methodology for the assessment of stream naturalness considering physical, biological and chemical factors. Physical factors consists of riffle and pool, river bed material, bank protection, floodplain vegetation and levee materials; biological factors are benthic macroinvertebrate, KSI (Korean Saprobic Index), and IBI (Index of Biological Integrity) and chemical factors are pH, DO (dissolved oxygen), and TP (total phosphorus). This procedure is applied to the Mokgamcheon. As a result, the downstream of Mokgamcheon (zone I) needs the prompt improvement of stream naturalness, compared to the others (zone II and III). This evaluation technique will be an effective tool to quantify the stream naturalness and can be used to set the target of stream restoration project.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1373-1378
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• 2017

This paper presents a basic ECU(Electronic Control Unit) hardware development procedure for the functional safety of in-vehicle network systems. We consider complete hardware redundancy as a safety mechanism for in-vehicle communication network under the assumption of the wired network failure such as disconnection of a CAN bus. An ESC (Electronic Stability Control) system is selected as an item and the required ASIL(Automotive Safety Integrity Level) for this item is assigned by performing the HARA(Hazard Analysis and Risk Assessment). The basic hardware architecture of the ESC system is designed with a microcontroller, passive components, and communication transceivers. The required ASIL for ESC system is shown to be satisfied with the designed safety mechanism by calculation of hardware architecture metrics such as the SPFM(Single Point Fault Metric) and the LFM(Latent Fault Metric).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.8 s.251
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• pp.993-1000
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• 2006

Operating experience of steam generators has shown that cracks of various morphology frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.5-13
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• 2005

Acoustic emission(AE) is defined as the transient elastic waves thar are generated by the rapid release of energy. The advantage of AE is that very early crack growth can be detected well before a highly stressed component may fail. At present, an exact diagnosis is the most reliable means for determining the soundness of structures during power plant operations. AE monitoring has been applied successfully in power plants to determine mechanical problems, pressure vessel integrity and external valves leaks, vacuum leaks, the onset of cavitation in pumps and valves, the presence of flow(or no flow) in piping and heat exchange equipment, etc. Acoustic emission(AE) technology has recently strengthened its application base, and practitioners' understanding of the technique's fundamentals. This paper introduces the methods of a survey and assessment on AE monitoring applications in nuclear, fossil and hydraulic power plant. The main objective of this paper was to obtain information on various applications of AE technology in power plant.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.17-26
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• 2011

CANDU reactor core is composed a few hundreds pressure tubes, which support and locate the nuclear fuels in the reactor. Each pressure tube provides pressure boundary and flow path of primary heat transport system in the core region. In order to guarantee the structural integrity of pressure tube flaws which can be found by in-service inspection, crack growth and fracture initiation assessment have to be performed. Stress intensity factors are important and basic information for structural integrity assessment of planar and laminar flaws (e. g. crack). This paper reviews and confirms the stress intensity factor of axial crack, proposed in CSA N285.8-05, which is an fitness-for-service evaluation code for pressure tubes in CANDU nuclear reactors. The stress intensity factors in CSA N285.8-05 were compared with stress intensity factors calculated by three methods (finite element results, API 579-1/ASME FFS-1 2007 Fitness-For-Service and ASME Boiler and Pressure Vessel Code Section XI). The effects of Poisson's ratio and anisotropic elastic modulus on stress intensity factors were also discussed.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.1001-1007
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• 1995

A Comprehensive Vibration Assessment Program (CVAP) has been performed for Yonggwang Nuclear Power Plant Unit 4 (YGN 4) in order to verify the structural integrity of the reactor internals for flow induced vibrations prior to commercial operation. The theoretical evidence for the structural integrity of the reactor internals and the basis for measurement and inspection are provided by the analysis. Flow induced hydraulic loads and reactor internals vibration response data were measured during pre-core hot functional testing in YGN 4 site. Also, the critical areas in the reactor internals were inspected visually to check any existence of structural abnormality before and after the pre-core hot functional testing. Then, the measured data have been analyzed and compared with the predicted data by analysis. The measured stresses are less than the predicted values and the allowable limits. It is concluded that the vibration response of the reactor internals due to the flow induced vibration under normal operation is acceptable for long term operation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.49-54
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• 2007

Structural integrity assessment technique for pavement system is studied considering the uncertainties among the material properties. The artificial neural networks technique is applied for the inverse analysis to estimate the elastic modulus based on the measured deflections from the FWD test. A computer code based on the spectral element method was developed for the accurate and fast analysis of the multi-layered soil structures, and the developed program was used for generating the training and testing patterns for the neural network. Neural networks was applied to estimate the elastic modulus of pavement system using the maximum deflections with and without the uncertainties in the material properties. It was found that the estimation results by the conventiona1 neural networks were very poor when there exist the uncertainties and the estimation results could be significantly improved by adopting the proposed method for generating training patterns considering the uncertainties among material properties.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2030-2036
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• 2016

This paper presents a hardware development procedure of the ASB(Active Seat Belt) control system to comply with ISO 26262. The ASIL(Automotive Safety Integrity Level) of an ASB system is determined through the HARA(Hazard Analysis and Risk Assessment) and the safety mechanism is applied to meet the reqired ASIL. The hardware architecture of the controller consists of a microcontroller, H-bridge circuits, passive components, and current sensors which are used for the input comparison. The required ASIL for the control systems is shown to be satisfied with the safety mechanism by calculation of the SPFM(Single Point Fault Metric) and the LFM(Latent Fault Metric) for the design circuits.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.122-128
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• 2019

Porcelain insulators have been used mainly for power line fixing and electrical insulation in transmission towers. Porcelain insulators have generally a 30 years desired life, but over 50% exceed their life expectancy. Since the damage to porcelain insulators is usually accompanied by enormous loss of human resource material, their efficient maintenance has emerged as an important issue. In this regard, this study applied a frequency response function (FRF) for integrity assessment of the insulator. The characteristics of the FRF according to damage types were identified and analyzed by the change in natural frequencies, curve shape, attenuation, and Nyquist diagram stability. The results showed significant differences in the FRF according to damage types, which can be used as basic data for the effective integrity assessment of porcelain insulators.