• Journal of Korean Society of Industrial and Systems Engineering
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• v.17 no.32
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• pp.209-220
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• 1994

In this paper, we study the timing and equipment of replacement. Those affect both available possibility and technological levels of new equipments in the future. These problems are classified according to technological levels and in consequence generated four circumstance. Models are formulated in this research. These are able to make us decision which we replace equipment at the first time. A method is suggested to find the optimal age for replacement at given each circumstance. A solution procedure and numerical example are given.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.647-652
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• 2008

Railway signal system has been more complex, larger and required high reliability. So, maintenance by experience must be changed to optimize maintenance program or introduced systematic method for estabilish new maintenance program. In this paper, we introduced the maintenance period decision method which are Age based method and Block replacement method based on the failure distribution for the equipment. So, we allocated optimum maintenacne period for the railway signal equipment using block replacement method.

• Journal of the Korea Safety Management & Science
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• v.8 no.2
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• pp.139-153
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• 2006

This paper deals with two forms of preventive replacement policy with minimal repair at failure. Those are, 1. the replacement policy I based on the cumulative operating time. 2. the replacement policy II based on the number of failures. The basic assumptions are; (1) the cost of minimal repair at failure is increasing with the number of failures since the last replacement, (2) the equipment fails stochastically with time.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.737-739
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• 1999

All equipment generally has a specified design service life. As an equipment nears the end of its design service life, replacement must be considered. In some cases, it is possible and more economical to continue the usage of the existing equipment for a longer period. So, replacement should be carefully decided considering the feasibility and economic benefits of the existing equipments' life extension. In this paper, assessment procedure for deciding between life extension and replacement of the electronic control system is presented with an application example. In particular estimation of the electronic control system's remaining life is focused on.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.4
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• pp.161-180
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• 2012

We develop some evaluation tool and indicators for the scores for medical equipment replacement in hospital. There has been no research for Korean hospitals although there are many for foreign medical institutions. In this paper, among many variables that were obtained from the previous studies, eleven variables are selected as indicators and tied as three groups. And then we obtain scores of medical equipments based on the weighted values of those indicators. We can make decisions whether we replace medical equipments or not by ranking the medical equipments based on the scores. This paper shows that we can make decisions to replace medical equipments very objectively and effectively using the evaluation tool and indicators we develop.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.217-223
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• 2006

When only partial information is available about equipment failures (installation date and amount, as well as failure and replacement rates), data on sufficiently large number of yearly populations of the components can be combined, and estimation of model parameters may be possible. The parametric models may then be used for forecasting of the system's short term future failure and for formulation of replacement strategies. We employ the Weibull distribution and show how we estimate its parameters from past failure data. Using Monte Carlo simulations, it is possible to assess confidence ranges of the forecasted component performance data.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.537-544
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• 2019

In currently electronic systems, the speed of information integration has increased due to the development of electronic technology. However, due to the increase in the number of parts and groups, the product structure has become complicated. In this paper, a study was conducted to evaluate quantitatively the replacement of a small equipment. First, the level of the replacement was determined through the algorithm for the replacement level of parts. Next, we defined the ease of detail replacment, and the factors for each detail replacement. In order to calculate the weighting of the detail ease, we performed the analysis of the replacement process of subcomponents of communication exchanger and defined the evaluation criteria. Finally, the completion of the evaluation check sheet and the evaluation score table.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.258-263
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• 2004

The purpose of this experiment is to modify diagnosis criterion of isothermal relaxation current(IRC) measurement equipment which is using for distribution cable diagnosis. We're using this system for several years in the field instead of DC leakage current measurement and lots of cables were replaced. But we have to investigate on the reliability of this equipment for our cables because we didn't carried out condition assessment of extracted cables after field diagnosis by this equipment. It is important thing for cable maintenance. If the replacement criterion is improper we can not prevent failures or will waste budget on account of replacement of the sound cables. In this paper we selected field installed cables and injected silicone fluid to the cables for insulation rehabilitation. In order to prove reliability of the diagnosis equipment we compared diagnosis results and AC breakdown strength according to operating time after silicone treatment. This is the results of the field test for 1 year.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.177-179
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• 2018

After Fukushima nuclear accident at 2011, nuclear industrial has been focused on operation and maintenance phase, not design and construction phase. Continued good operating performance of nuclear power plants has been the best critical issue to nuclear utilities. Replacement for complete components as well as parts of components is being procured because nuclear utilities must maintain safety and reliability of operating nuclear power plants. However, many suppliers and manufacturers are giving up a nuclear quality assurance program under reduction in new construction of nuclear power plants. It is able to be increased difficulty in procuring spare parts to support operations and maintenance of nuclear power plants. Over 20% of nuclear power plant equipment in some countries is obsolete. Owing to obsolescence of nuclear safety-related items and/or withdrawing a nuclear quality assurance program of suppliers and manufactures, some replacement item and part might be procured to the item not covered by appendix B to USNRC 10 CFR Part 50. Under various methods of the nuclear repair and replacement methodology, utilities are supposed to establish a typical program for a repair and replacement of an electrical equipment and its parts in conjunction with a nuclear quality assurance. Concerning this typical program, this study suggests the repair and replacement methodology of electrical equipments used in nuclear power plants by procurement of a power supply, based on nuclear regulations, codes, standards, guidelines, specific and general technical information, etc..

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.287-295
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• 2022

The GNSS coordinate time series is used as important data for geophysical analysis such as terrestrial reference frame establishment, crustal deformation, Earth orientation parameter estimation, etc. However, various factors may cause discontinuity in the coordinate time series, which may lead to errors in the interpretation. In this paper, we describe the discontinuity in the coordinate time series due to the equipment replacement for domestic GNSS stations and discuss the change in movement magnitude and velocity vector difference in each direction before and after discontinuity correction. To do this, we used three years (2017-2019) of data from 40 GNSS stations. The average magnitude of the velocity vector in the north-south, east-west, and vertical directions before correction is -12.9±1.5, 28.0±1.9, and 4.2±7.6 mm/yr, respectively. After correction, the average moving speed in each direction was -13.0±1.0, 28.2±0.8, and 0.7±2.1 mm/yr, respectively. The average magnitudes of the horizontal GNSS velocity vectors before and after discontinuous correction was similar, but the deviation in movement size of stations decreased after correction. After equipment replacement, the change in the vertical movement occurred more than the horizontal movement variation. Moreover, the change in the magnitude of movement in each direction may also cause a change in the velocity vector, which may lead to errors in geophysical analysis.