• Journal of the Korean Society for Railway
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• v.4 no.3
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• pp.116-122
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• 2001

As freight traffic becomes heavier, the high speed of existing freight cars is essential, instead of the construction of a new railway. The high speed can be achieved by the modifications of freight bogie design. In this paper, an analytical model of freight bogie is developed to decide the critical speed. The dynamic responses of the analytical model are compared with the experimental data from a running test of freight bogie and showed good agreements between them. The analytical model is used to find the design of freight bogie. The parameter studies show that the reduction of wheelset mass ratio and the increase of the axle distance of freight bogie can increase the critical speed, but the primary lateral stiffness has little effects on the critical speed. And this study also shows that smaller wheel conicity deteriorates the running safety of freight car, which means that the overhauling of the wheel of freight bogie should be done regularly.

• Journal of the Korea Safety Management & Science
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• v.8 no.4
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• pp.25-37
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• 2006

Critical incident can be happened at any time, any places without any pre-notification. For minimizing the loss of the life safety, financial and so on caused by the risk, most of company needs a system what can activate the critical incident management plan to prevent, plan for and respond to events that become critical incident. But a lot of company still don't have such a detailed system in our country and almost company has no effective training way for to boot. This paper shows the way to activate the risk management system to work efficiently the plan. The training way, proposed by this paper, is a incident command simulator based on virtual reality and scenario generation software.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2638-2651
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• 2020

Nozzle corner cracks present at the intersection of reactor pressure vessels (RPVs) and inlet or outlet nozzles have been a persistent problem for a number of years. The fracture analysis of such nozzle corner cracks is very important and critical for the efficient design and assessment of the structural integrity of RPVs. This paper aims to perform an engineering critical assessment of RPVs with nozzle corner cracks subjected to several transients accompanied by pressurized thermal shocks. The critical crack size of the RPV model with nozzle corner cracks under transient loading is evaluated on failure assessment curve. In particular, the influence of cladding on the crack initiation of nozzle corner crack under thermal transients is studied. The influence of primary internal pressure and secondary thermal stress on the stress field at nozzle corner and SIF at crack front is analyzed. Finally, the influence of different crack size and crack shape on the final critical crack size is analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.345-354
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• 2018

This study was conducted to identify the levels of patient safety culture, critical thinking disposition, and patient safety nursing activities and determine the factors affected by patient safety nursing activities among nurses in comprehensive nursing care service wards. Subjects consisted of 150 nurses from general hospitals in B city, Korea, and data were analyzed using the SPSS Win 21.0 program. The mean scores of awareness of patient safety culture, critical thinking disposition, and patient safety nursing activities were $3.32{\pm}0.32$, $3.50{\pm}0.31$, and $4.28{\pm}0.46$, respectively. The awareness of patient safety culture was significantly different by clinical career in the present unit (F=4.79, p=0.001). The critical thinking disposition was significantly different by age (F=3.89, p=0.010) and position (F=6.40, p=0.002). There were differences in the scores of patient safety nursing activities according to position (F=3.19, p=0.044). Additionally, hospital environment (${\beta}=0.25$, p=0.014), supervisor attitude (${\beta}=0.20$, p=0.046), and position (${\beta}=0.14$, p=0.040) accounted for a 44.4% variance in patient safety nursing activities. To promote patient safety nursing activities in comprehensive nursing care service wards, positive awareness of the hospital's safety environment and support from the manager are required.

• Journal of the Korea Safety Management & Science
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• v.16 no.1
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• pp.69-77
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• 2014

The environment and requirements of modern war fields have been affected and thus changed by a variety of issues. To this end, the development of safety-critical weapon systems frequently need to meet those changes even in the operational phase. The necessity of the changes may be due to the preparation for mass-production or the request originated from the user military forces. To meet such a need can be even tougher in the development of safety-critical weapon systems since the integration of the requirements for both systems design and systems safety would make it troublesome. To handel the matter in this paper, utilization of architecture DB is proposed. Specifically, the situation in demand has first been analyzed and then a problem-solving process to accommodate the design changes has been constructed. In doing so, the concept of the aforementioned integration is particularly focused on the functional architecture, which could be a core concept of our approach to solving the problem. The result of a case study demonstrating the method studied using a computer-aided systems engineering tool is also presented.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.76-87
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• 2010

According to the new rules and regulations (New SOLAS), major safety critical systems are to be designed to be redundant, which is called 'Redundancy Design'. This paper was to quantitatively analyze the degree of influence of the redundancy design applied to major safety critical systems using IMO's FSA(formal Safety Assessment) method. For the purpose of this study, the diesel engine system, which is actually one of major safety critical systems, was dealt with FMEA, FTA and ETA technique. In addition, whether the redundancy was met or not was verified and the degree of safety, or redundancy, was represented in terms of reliability. In conclusion, the safety of propulsion systems is possibly assessed systematically by estimating the risk level in terms of frequency and fatality.

• Proceedings of the Korean Society for Quality Management Conference
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• 2004.04a
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• pp.114-119
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• 2004

Software verification and validation(V&V) is a means to develop high-quality software and assure safety and reliability for software. Also, we can achieve the desired software quality through systematic V&V activities. The software to be applied safety critical system like nuclear power plants is required to setup the V&V methodology that comply with licensing requirements for nuclear power plants and should be performed V&V activities according to it. In this paper, we classified safety-critical, safety-related and non-safety for software according to safety function to be peformed and define V&V activities to be applied software grade. Also, we defined V&V activities, procedures and documentation for each phase of software development life cycle and showed techniques and management to perform V&V. Finally, we propose the V&V framework to be applied software development of SMART(System-integrated Modular Advanced ReacTor) MMIS (Man-Machine Interface System) and to comply with domestic licensing requirements.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.834-841
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• 2022

System thermal-hydraulic (STH) code is adopted for nuclear safety analysis. The critical flow model (CFM) is significant for the accuracy of STH simulation. To overcome the defects of current CFMs (low precision or long calculation time), a CFM based on a genetic neural network (GNN) has been developed in this work. To build a powerful model, besides the critical mass flux, the critical pressure and critical quality were also considered in this model, which was seldom considered before. Comparing with the traditional homogeneous equilibrium model (HEM) and the Moody model, the GNN model can predict the critical mass flux with a higher accuracy (approximately 80% of results are within the ±20% error limit); comparing with the Leung model and the Shannak model for critical pressure prediction, the GNN model achieved the best results (more than 80% prediction results within the ±20% error limit). For the critical quality, similar precision is achieved. The GNN-based CFM in this work is meaningful for the STH code CFM development.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1414-1419
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• 2011

In this paper we study the modeling to quantitatively assess the failure rate of USN system designed for fault-tolerant architecture, aiming at applying the world's best domestic USN technology to safety-critical railways. In order to apply the USN system to the safety-critical field like a train control sector that the failures of controllers may cause severe railway accidents such as train collision and derailment, the quantitative reliability and safety evaluation recommended in IEC 62278 must be preceded. We also develop the evaluation model for overall system failure rate for the distributed network structure, which is the characteristics of USN system. Especially, we allocate reliability targets to component units, and present an availability evaluation plan through the plan on the quantitative achievement of failure rate for sensor nodes, gateways, radio-communication network and servers, along with the failure rate model of the overall system considering network operational features.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.201-203
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• 2007

Safety critical systems are those in which a failure can have serious and irreversible consequences. Nowadays digital technology has been rapidly applied to critical system such as railways, airplanes, nuclear power plants, vehicles. The main difference between analog system and digital system is that the software is the key component of the digital system. The digital system performs more varying and highly complex functions efficiently compared to the existing analog system because software can be flexibly designed and implemented. The flexible design make it difficult to predict the software failures. This paper reviews safety standard and criteria for safety critical system such as railway system and suggests software development methodology for more detail description.