• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.2
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• pp.84-94
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• 2018

In recent years, the diminishing of operation and maintenance cost using advanced maintenance technology is attracting many companies' attention. Especially, the heavy machinery industry regards it as a crucial problem since a failure of heavy machinery requires high cost and long downtime. To improve the current maintenance process, the heavy machinery industry tries to develop a methodology to predict failure in advance and to find its causes using usage data. A better analysis of failure causes requires more data so that various kinds of sensor are attached to machines and abundant amount of product usage data is collected through the sensor network. However, the systemic analysis of the collected product usage data is still in its infant stage. Many previous works have focused on failure occurrence as statistical data for reliability analysis. There have been less works to apply product usage data into root cause analysis of product failure. The product usage data collected while failures occur should be considered failure cause analysis. To do this, this study proposes a methodology to apply product usage data into failure cause analysis. The proposed methodology in this study is composed of several steps to transform product usage into failure causes. Various statistical analysis combined with product usage data such as multinomial logistic regression, T-test, and so on are used for the root cause analysis. The proposed methodology is applied to field data coming from operated locomotive and the analysis result shows its effectiveness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.366-372
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• 2020

The Army's rocket missile is a one-shot weapon system, which is produced and used for only one mission, and requires high reliability. While reliability analysis with failure data can result in underestimation of the life distribution, reliability analysis with all the non-failure data can result in overestimation of the life distribution. Under or overestimation of the life distribution can lead to cost increase by early disposal or complete observation of all rocket missiles. In order to overcome this problem, the Army suggests the guideline of the number of samples from non-failure data for reliability analysis with failure data. However, the currently used sampling method can generate errors for predicting the failure rate. To solve this problem, this study proposes a new sampling procedure for predicting a future failure rate using non-failure data. The comparison test between the currently used sampling method and the proposed sampling method is conducted and the result shows that the proposed sampling method can predict the future failure rate more accurately.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.223-226
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• 2009

Various database and analysis system has been used for the cost effective maintenance of distribution facility but it is not effective because of the lack of interconnection among these systems. In order to overcome this problem this paper proposes reliability centered maintenance system based on the on-line monitoring of distribution system through intelligent distribution equipment. This system is made by the interconnection of distribution automation system, asset management system, failure analysis system and failure mode effect analysis system.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1371-1379
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• 2013

Application of induction machines in wind turbine driven generators is a good alternative due to their good characteristics such as efficiency, reliability and low cost. Nevertheless, when isolated operation is required, the application of external capacitive bank, connected to the stator windings, to provide self-excitation results in a rather complex analysis. This paper presents an analysis of self-excited induction generator connected to a load either directly or by an intermediate of a power converter. At first a dynamic model of the induction generator accounting for magnetic saturation is developed. Then a number of balanced and unbalanced capacitors, passive and active loads are verified. Experimental results obtained from laboratory tests are compared to those simulated; the two are shown to be in good agreement.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.203-207
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• 2009

WiBro(Mobile WiMAX) has gained momentum as a top candidate to deliver the dream of full mobile wireless internet. To save cost and time in WiBro network design, simulation tool has to deploy powerful and useful analysis functions. If path loss model is more accurate, the reliability of analysis result of simulation tool will be much improved. So we emphasize on the importance of pathloss model in WiBro network design in this paper. For this, we introduce to three kinds of pathloss models(SUI, SCM, SCM-E) supposed properly models in WiBro RF (Radio Frequency) environment. Also we treat from basic theory to practical substance on the pathloss model to adopt WiBro network design/optimization. Finally, we describe about wireless network analysis tool named 'CellPLAN(R)' and techniques possible to improvethe accuracy of pathloss model.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.985-990
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• 2005

The success of road transportation, in dominating the surface movement of freight, is now threatened by increased traffic congestion, falling average motorway speed and rising in logistics costs, oil price. Due to the necessity for an effective transport system, we need to improve domestic transport infrastructure to reduce logistics cost by shifting to rail system. To analysis the demand characteristics in advance against these hypothetical circumstances, Stated Preference, which is called SP, approaches have been adopted to analysis the shipper's mode choice behaviors as RP(Revealed Preference) approaches are not appropriate. The results also indicate that the most effective policy to divert the freight volume from road to railway is to reduce freight rates for the railway with improved reliability.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.485-490
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• 2009

The present study has been conducted to accomplish the investment and analysis, to make the construction manuals, to draw the standards, and to build quality and standards informations of the plumbing/drainage facilities materials. The application plan and the anticipation effect of this results include as follows. (1) The investment and analysis of the plumbing/drainage facilities materials is able to suggest the technology trends and the trends analysis in the construction materials. (2) The quality and standards informations of the plumbing/drainage facilities materials are possible to be the construction faculty and the cost/energy reduction in the construction materials. (3) The standards methods of the plumbing/drainage facilities materials are useful for the reliability guarantee and quality escalation in the construction materials. (4) The standard manuals of the plumbing/drainage facilities materials are applied to the specifications in the construction materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.306-312
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• 1992

The prevention of roll breakage in hot rolling process is improtant to reduce maintenance cost and production loss. Rolling conditions such as the roll force and torque have been intensively studied to overcome the roll breakage. in the present work, a model for life prediction of work rolls under working condition was developed and discussed. The model consists of stress analysis, crack propagation, wear and fatigue calculation model. Roll life can be predicted by stress, crack depth and fatigue damage calculated from this model. The reliability of stress analysis is backed up by the FEM analysis. From the result of simulation using by pressent model, although the fatigue damage of back up roll reachs 80% of practical limit, that of workroll was less than 40%. In edge section of workroll stress amplification is found by wear and bender effect. We can judge that workroll failures are not due to fatigue damage, crack propagation by bending stress but stress amplification by wear and bender in present working condition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.156-157
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• 2016

Construction projects have shown a dramatic increase in size and complexity during the recent years that precise management has been recognized as one of key factors leading the project to success. It has been investigated that management in construction sites is generally done based on the experience of site engineers. Such experience based decision making lacks reliability that could bring disastrous results such as delay and cost overruns. The purpose of this study is to suggest a process progress pattern analysis method that is expected to be used as an objective reference for site managers to aid the decision making done regarding process progress management.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.284-291
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• 1999

The reliability analysis is of great importance in their design since offshore towers are high-cost and high-risk structures. The design of platforms in the marine environment depends on results of the dynamic behavior of the structure during earthquakes and storm wave conditions. this paper presents results of an analytical study on evaluating dynamic response of steel jacket modelled by space frame elements. program $\boxDr$OFSPC$\boxUl$for the linear and nonlinear dynamic analysis of steel jacket platform has been developed using FORTRAN 90 programing language through the present study. Free vibration and dynamic behavior of steel jackets under regular and irregular wave and earthquake force are investigated using this program