• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.44
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• pp.263-271
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• 1997

This paper presents a preventive maintenance model for determining the preventive replacement period of a system in which a failure rate is affected by the cumulative damage of fault and inspection. Especially, the failure rate function is considered to be a function of the cumulative damage of the fault and inspection time. Types of replacement considered are preventive replacement and failure replacement. Failure rate and expected cost function between replacement are derived. An optimal policy is obtained that minimizes the average cost per unit time for preventive replacement, failure replacement, inspection and repair.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.95-105
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• 2009

In this study, we presented the periodic inspection method of the Certified Missile Round Concepts usuing M&S(Modeling and Simulation) techniques. Firstly, We drew up the scenario from the application concepts and the predicted dormant reliability Secondly, we performed the modeling for a simulation program based on the scenario. Lastly we embodied the simulation program. After comparing and examining the difference between the simulation results and the theoretical estimates, we present the best periodic inspection plan for achieving the probability of success.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.372-372
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• 1994

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.8
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• pp.898-906
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• 1999

A control structure is introduced for the purpose of rejecting periodic (or repetitive) disturbances on a tracking system. The objective of the proposed structure is to drive the output of the system to the reference input that will result in perfect following without any changing the inner configuration of the system. The structure includes an adaptation block which learns the dynamics of the periodic disturbance and forces the interferences, caused by disturbances, on the output of the system to be reduced. Since the control structure acquires the dynamics of the disturbance by on-line adaptation, it is possible to generate control signals that reject any slowly varying time-periodic disturbance provided that its amplitude is bounded. The artificial neural network is adopted as the adaptation block. The adaptation is done at an on-line process. For this , the real-time recurrent learning (RTRL) algoritnm is applied to the training of the artificial neural network.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.25-30
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• 2013

The periodic inspection of piping and pressure vessels welds in nuclear power plant has to provide reliable result related to weld flaws, such as location, maximum amplitude response, ultrasonic length, height and finally the nature or flaw pattern. The founded flaw in ultrasonic inspection is accepted or rejected based on these data. Specially, the amplitude of flaw response is used as basic parameter for flaw sizing and it may cause some deviation in length sizing result. Currently the ultrasonic inspections in nuclear power plant components are performed by specific inspection procedure which describing inspection technique include inspection system, calibration methodology and flaw characterizing. To perform ultrasonic inspection during in-service inspection, reference gain should be established before starting ultrasonic inspection by the requirement of ASME code. This reference gain used as basic criteria to evaluate flaw sizing. Sometimes, a little difference in establishing reference gain between calibration and field condition can lead to deviation in flaw sizing. Due to this difference, the inspection result may cause flaw sizing error. Therefore, the objective of this study is to compare and evaluate the ultrasonic amplitude difference between air filled and water filled pipe in nuclear power plant. Additionally, the accuracy of flaw sizing is estimated by comparing both conditions.

• Journal of the military operations research society of Korea
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• v.18 no.1
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• pp.110-127
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• 1992

In the preventive replacement policies of system that the failure can be detected through only periodic inspection, there is a penalty cost associated with the lapsed time between system failure and its detection. The system under study is replaced if the system fails before $n^{th}$ inspection, otherwise, preventive replacement is performed at the $n^{th}$ inspection. The decision variables are the inspection interval and the period of preventive replacement. This study presents the optimal preventive replacement policy that minimizes the long-run expected cost per unit time.

• Journal of Korean Institute of Industrial Engineers
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• v.11 no.1
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• pp.3-10
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• 1985

Periodic replacement policies are proposed for a system whose repair cost, when it fails, can be estimated by inspection. The system is replaced when it reaches age T (Policy A), or when it fails for the first time after age T (Policy B). If it fails before reaching age T, the repair cost is estimated and minimal repair is then undertaken if the estimated cost is less than a predetermined limit L; otherwise, the system is replaced. The expected cost rate functions are obtained, their behaviors are examined, and ways of obtaining optimal T and L are explored.

• Journal of Platform Technology
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• v.9 no.4
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• pp.51-59
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• 2021

In this paper, we propose a location-based service that the user's location is known by connection history to WI-FI AP installed in a facility known its location previously. The location-based service proposed in this paper manages job processing states of technicians who inspect and maintain the facility like elevator by using worker's location and arrival time information. The job scheduling management method proposed in this paper is based on previously scheduled arrival time and actual arrival time to a target facility. And we experimentally implemented the inspection and maintenance system of an elevator to show the feasibility of job schedule management based on location and arrival time information acquired from Wi-Fi AP connection history. Our experimental implementation shows that our proposed method is usefulness in the field of the inspection and maintenance of a facility.

• Journal of Platform Technology
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• v.10 no.1
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• pp.11-19
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• 2022

In this paper, we propose a location-based service that the user's location is known by connection history to WI-FI AP installed in a facility known its location previously. The location-based service proposed in this paper manages job processing states of technicians who inspect and maintain the facility like elevator by using worker's location and arrival time information. The job scheduling management method proposed in this paper is based on previously scheduled arrival time and actual arrival time to a target facility. And we experimentally implemented the inspection and maintenance system of an elevator to show the feasibility of job schedule management based on location and arrival time information acquired from Wi-Fi AP connection history. Our experimental implementation shows that our proposed method is usefulness in the field of the inspection and maintenance of a facility.

• International Journal of Safety
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• v.6 no.2
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• pp.13-16
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• 2007

This study focuses on the trends and issues of improving safety management of elevators in Korea. Frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analyzed based on the statistical data and social cost due to a variety of related fields in managing elevator safety was estimated first. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system. The role of certification and supervision is particularly addressed to reduce the related accidents and the social cost. The effectiveness of such procedures can be found from the results of simple statistical analysis.