• Journal of Korean Society of Archives and Records Management
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• v.16 no.2
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• pp.29-55
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• 2016

Korean public organizations create electronic documents through electronic document management systems under the e-Government scheme. A majority of these public documents are saved in vendor-dependent file formats, mainly HWP. Vendor-dependent formats can be opened only with specific software, which requires purchase. As the license does not guarantee compatibility between past and future versions, interoperability problems occur in long-term preservation, which need to be solved. Any error from the elimination of styles or no matching elements in document definition during conversion from vendor-dependent formats to the XML-based standard exchange format leads to file open failure or the modification of original documents. This study introduces the Open Document Format (ODF) and investigates the effects of adopting ODF in the creation, exchange, management, and preservation of public records.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.121-127
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• 2020

Since the Fukushima nuclear accident in 2011, the public were concerned about the safety of Nuclear Power Plants (NPPs) in extreme natural disaster situations, such as earthquakes, flooding, heavy rain and tsunami, have been increasing around the world. Accordingly, the Stress Test was conducted in Europe, Japan, Russia, and other countries by reassessing the safety and response capabilities of NPPs in extreme natural disaster situations that exceed the design basis. The extreme natural disaster can put the NPPs in beyond-design-basis conditions such as the loss of the power system and the ultimate heat sink. The behaviors and capabilities of NPPs with losing their essential safety functions should be measured to find and supplement weak areas in hardware, procedures and coping strategies. The Loss of Ultimate Heat Sink (LUHS) accident assumes impairment of the essential service water system accompanying the failure of the component cooling water system. In such conditions, residual heat removal and cooling of safety-relevant components are not possible for a long period of time. It is therefore very important to establish coping strategies considering all available equipment to mitigate the consequence of the LUHS accident and keep the NPPs safe. In this study, thermal hydraulic behavior of the LUHS event was analyzed using RELAP5/Mod3.3 code. We also performed the sensitivity analysis to identify the effects of the operator recovery actions and operation strategy for charging pumps on the results of the LUHS accident.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4163-4170
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• 2013

The recent studies indicated that the major sources of the failure in carrying out the programs of weapon systems development would be the unsatisfaction of the required key performance and also the use of premature technology. As such, to manage the risk during the weapon systems development, the use of the technical performance measurement (TPM) and the technology maturity assessment (TMA) turned out to be necessary. However, the TPM studied so far seems to cover the assessment of performance at the component level only, and thus is insufficient in considering the system integration effect. On the other hand, the system readiness level (SRL) method has been presented by reflecting the effect on system integration, but the system performance and maturity has not been considered. To overcome this, a measurement method is proposed in the paper by utilizing the combined system readiness level and achieved technical performance at the system level. This system performance measure can be useful in managing the risk in the weapon systems development.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.85-99
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• 1998

This paper describes an experimental study to examine collapse causes of the lifting cable due to brittle failure of an fitting anchor under the lifting works. Also, in this study an collapse mechanism that was obtained from stress analysis was compared with an actual collapse procedure. Fractographical analysis as well as chemical component test, tension test and Charpy V-Notch impact test for the fractured steel members were carried out. And then, its results were compared with that of normal steel members. Circumferential surface flaws were developed at internal facets of the fitting anchor before tensile stress occurred. Hence, a higher stress than nominal stress was occurred at flaws by stress concentration at the crack tip. Also, stress intensity factor of members increased by crack size of the potential flaws. Because the stress intensity factor at the crack tip was greater than critical values(fracture toughness), brittle fracture occurred under the lifting works. It is judged that the main collapse of the lifting cable is due to brittle fracture of the fitting anchor.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.396-410
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• 2018

To assist operators to properly assess the current situation of the plant, accurate fault diagnosis methodology should be available and used. A reliable fault diagnosis method is beneficial for the safety of nuclear power plants. The major idea proposed in this work is integrating the merits of different fault diagnosis methodologies to offset their obvious disadvantages and enhance the accuracy and credibility of on-line fault diagnosis. This methodology uses the principle component analysis-based model and multi-flow model to diagnose fault type. To ensure the accuracy of results from the multi-flow model, a mechanical simulation model is implemented to do the quantitative calculation. More significantly, mechanism simulation is implemented to provide training data with fault signatures. Furthermore, one of the distance formulas in similarity measurement-Mahalanobis distance-is applied for on-line failure degree evaluation. The performance of this methodology was evaluated by applying it to the reactor coolant system of a pressurized water reactor. The results of simulation analysis show the effectiveness and accuracy of this methodology, leading to better confidence of it being integrated as a part of the computerized operator support system to assist operators in decision-making.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.97-102
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• 2012

Alternate alternating current (AAC) is used in nuclear power plants (NPPs) in order to cope with station black outs (SBOs). AAC has been provided using diesel engine drive types in Korea's NPPs. The structure of gas turbine generators (GTGs) is simpler than that of diesel generators (DGs), and GTGs have the advantage of longer maintenance intervals. However, GTG-AAC was not used in NPPs in Korea because of the lack of operation/maintenance experience. The purpose of this paper is to analyze the safety of APR+ considering a diversity of AAC types. This paper analyzes reliability data, mechanical specifications of DGs and GTGs, and the sensitivity of core damage frequency to the ACC type.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.91-96
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• 2012

The retract actuator makes the landing gear retract or extend during take-off and landing of an aircraft. To prevent folding of landing gear that has remained in the extended state because of an unexpected external disturbance, an internal locking device is applied to the retract actuator. The locking device is restrained with another internal component by oil pressure supplied to the retract actuator, and this restraint makes the locking of the actuator possible. Because locking and unlocking are repeated during retraction and extension of the landing gear, the locking device takes repeated identical loads, and the possibility of fatigue failure exists. In this study, the process and results of fatigue analysis for the locking device are presented, and the appropriateness of the analysis result is verified using a fatigue test.

• Nuclear Engineering and Technology
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• v.40 no.1
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• pp.49-68
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• 2008

The purpose of this paper is to extensively review the condition monitoring (CM) techniques using empirical models in an effort to reduce or eliminate unexpected downtimes in general industry, and to illustrate the feasibility of applying them to the nuclear industry. CM provides on-time warnings of system states to enable the optimal scheduling of maintenance and, ultimately, plant uptime is maximized. Currently, most maintenance processes tend to be either reactive, or part of scheduled, or preventive maintenance. Such maintenance is being increasingly reported as a poor practice for two reasons: first, the component does not necessarily require maintenance, thus the maintenance cost is wasted, and secondly, failure catalysts are introduced into properly working components, which is worse. This paper first summarizes the technical aspects of CM including state estimation and state monitoring. The mathematical background of CM is mature enough even for commercial use in the nuclear industry. Considering the current computational capabilities of CM, its application is not limited by technical difficulties, but by a lack of desire on the part of industry to implement it. For practical applications in the nuclear industry, it may be more important to clarify and quantify the negative impact of unexpected outcomes or failures in CM than it is to investigate its advantages. In other words, while issues regarding accuracy have been targeted to date, the concerns regarding robustness should now be concentrated on. Standardizing the anticipated failures and the possibly harsh operating conditions, and then evaluating the impact of the proposed CM under those conditions may be necessary. In order to make the CM techniques practical for the nuclear industry in the future, it is recommended that a prototype CM system be applied to a secondary system in which most of the components are non-safety grade. Recently, many activities to enhance the safety and efficiency of the secondary system have been encouraged. With the application of CM to nuclear power plants, it is expected to increase profit while addressing safety and economic issues.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.123-128
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• 2021

As the spread of DC power distribution systems increases, the occurrence of failures and fire accidents are also increasing. In particular, the ESS fire accident, which is a component of the smart grid, and the fire accident of the solar power system, which is a direct current system, are caused by problems in the electrical connection between system components as the supply of new and renewable energy rapidly increases and old facilities increase. An arc that can cause a direct fire by releasing the induced light and heat has been pointed out as one of the causes of fire. Therefore, the problem of such an arc defect is that it is impossible to block an arc accident in advance with the existing overcurrent circuit breaker and earth leakage circuit breaker. In this paper, we intend to develop a test equipment that satisfies international standardization and to develop a DC arc generator to protect against failure and fire caused by arcing.

• Wind and Structures
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• v.28 no.3
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• pp.181-190
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• 2019

Light-frame wood structures have the ability to carry gravity loads. However, their performance during severe wind storms has indicated weakness with respect to resisting uplift wind loads exerted on the roofs of residential houses. A common failure mode observed during almost all main hurricane events initiates at the roof-to-wall connections (RTWCs). The toe-nail connections typically used at these locations are weak with regard to resisting uplift loading. This issue has been investigated at the Insurance Research Lab for Better Homes, where full-scale testing was conducted of a house under appropriate simulated uplift wind loads. This paper describes the detailed and sophisticated numerical simulation performed for this full-scale test, following which the numerical predictions were compared with the experimental results. In the numerical model, the nonlinear behavior is concentrated at the RTWCs, which is simulated with the use of a multi-linear plastic element. The analysis was conducted on four sets of uplift loads applied during the physical testing: 30 m/sincreased by 5 m/sincrements to 45 m/s. At this level of uplift loading, the connections exhibited inelastic behavior. A comparison with the experimental results revealed the ability of the sophisticated numerical model to predict the nonlinear response of the roof under wind uplift loads that vary both in time and space. A further component of the study was an evaluation of the load sharing among the trusses under realistic, uniform, and code pressures. Both the numerical model and the tributary area method were used for the load-sharing calculations.