• Water for future
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• v.29 no.3
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• pp.197-205
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• 1996

Flow carrying capacity of water distribution systems is getting reduced by deterioration of pipes in the systems. The objective of this study is to develop a managerial decision-making model for the rehabilitation of water distribution systems with a minimum cost. The decisions made by the model also satisfy the requirements for the discharge and pressure at demanding nodes in the system. The replacement cost, pipe break repair cost, and pumping cost are considered in the economic evaluation of the decision along with the break ratio and interest ratio to determine the optimal replacement time for each pipe. Then, the hydraulic integrity of the water distribution system is checked for the decision by a pipe network simulator, KYPIPE, if the discharge and pressure requirements, the decision made for the optimal replacement time is revised until the requirements are satisfied. The model is applied to an existing water distribution system, the Metropolita Water Supply Project (1st Phase). The result shows that the decisions for the replacement time determined by the economix analysis are accepted as optimal and the hydraulic integrity of the system is in good condition.

• Asia Marketing Journal
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• v.7 no.2
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• pp.47-69
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• 2005

With the explosive growth of mobile products industry, tons of newer versions of products are putting on the market. From the marketer's perspective, understanding consumers' replacement purchases, especially the replacement timing, is essential to product planning and selling. This study presents an approach to finding out factors influencing the timing of buyers' replacement purchases of cell phones, using duration analysis; a hazard function specification is applied to describe consumers' replacement timing decision. Based on the data collected from a mobile telecommunication company, five categories of factors have been inspected. These are consumer's innovative service usage, data service usage, voice service usage, participation in loyalty programs, and the demographic characteristics. The results of the study are as follows. Firstly, the positive coefficient of 'the number of related services used' suggests that the consumers who have more usage knowledge tend to replace faster. Secondly, customers participating in the membership service are positively associated with early replacement purchases. Lastly, younger customers(vs. older) and male(vs. female) customers turned out to replace cell phones earlier.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.189-190
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• 2019

본 연구에서는 명절이 소비자들의 제품 교체주기에 영향을 미치는지를 탐색하기 위해 중국 온라인 휴대폰 판매 데이터를 바탕으로 명절 시기별 구매간격 차이검증을 통해 실증적으로 분석하고자 하였다. 분석결과, 명절시점과 평상시점 간에 제품 구매간격의 차이가 있는 것으로 나타났다. 즉, 명절시점이 평상시점보다 제품 교체주기가 짧은 것으로 나타나 명절효과가 있음을 증명하였다. 한편, 춘절, 노동절, 국경절 등 명절유형 간 제품 구매간격의 차이는 나타나지 않았다. 이는 기업이 명절시점을 활용하여 교체 가능성이 높은 소비자를 선별적으로 공략한다면 더 높은 성과를 얻을 수 있음을 시사한다. 본 연구의 결과는 실무적으로 볼 때 기업으로 하여금 교체확률이 높은 시기에 마케팅을 집중할 수 있도록 할 수 있을 것이며, 학술적으로는 제품 구매 간격에 영향을 미치는 구매시점 효과 중 명절효과를 온라인상의 고관여 제품에 적용하여 탐구했다는 공헌점이 있다.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.535-541
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• 2020

A conventional elastic material replacement and performance evaluation are very complicated and time-consuming, and it is difficult to know when to replace the elastic material in advance. By comparing with the product limit and the functional limit, the necessity of elastic material replacement and the improvement of track support stiffness according to replacement can be immediately demonstrated based on experimental data. Using an evaluation system of track support stiffness, the performance evaluation data for elastic materials obtained through field tests using software for track support stiffness is integrated and managed on the administrator's computer. Therefore, the replacement plan is established and maintenance history is managed by identifying the replacement time and location of elastic materials. It is possible to evaluate the performance and condition of the elastic material at the various points during the working time of the track inspection and the track performance (track support stiffness) and durability of the elastic material (aging level, spring stiffness variation rate, etc.) at the operation condition. The elastic material could be replaced timely, and the deterioration of the elastic material can be continuously monitored.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.3
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• pp.279-285
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• 2009

In this study, applied to the industrial water service, it is verified feasibility of break-even analysis method which has not been introduced in Korea. The On-san water pipeline of 7.1km among the Ul-san industrial water service is selected and the optimal replacement time calculated by break-even analysis method is year 2033 to 2044 which will be 53 to 67 years since the pipes were buried. If indirect cost such as the value of lost water and traffic disruption, service interruption, etc. is calculated as 30 and 100% of the direct cost, the financially optimum replacement time is advanced 3 to 9 years. These ways present rational criteria to establish long-term plan for budget and to execute the limited budget efficiently.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.25-31
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• 1995

발전 Plant는 고온.고압하에서 장기간 사용되며 파손발생시는 대형 사고로 확대되므로 경년에 따 른 운용기술의 확보가 현안 과제이다. 즉, 현재의 설비를 그대로 사용할 것인가 \ulcorner 또는 교체하여 야 할 것인가\ulcorner 그대로 사용한다면 취약부위는 어디이며 언제 보수하여야 하는가 \ulcorner 또 교체한다 면 그 시기는 언제인가 \ulcorner 에 대한 기술적 예측이 필요하다 수명예측기술은 이러한 의문에 대한 해답을 주는 Plant 설비 운용기술중 가장 최신 기술분야의 하나이다. 본고에서는 보일러 부분중 가장 사용조건이 가혹하고 교체하는데 많은 비용과 시간이 소용되는 최종과열기를 대상으로 균열 전파에 의한 수명예측에 관하여 기술코자 한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.48-53
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• 2010

In this paper, we develop the intelligent remote dust chamber bag control system which is combination of the advanced IT and traditional dust chamber based on event. At first, the message format is defined for the efficient dust chamber bag information transmission using power line communication. Also, we define the data types to logically model the dust chamber and the dust chamber bag, and they are logically modeled using XML and object-oriented modeling method. In addition to, we apply the case-based reasoning for showing the dust chamber bag exchange time intelligently to user at real-time using casebase, that is collected by case or case-based reasoning result, and that is described using XML.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.93-96
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• 2008

If a fluorescent lamp be used too much time, the filmy part of electronic emission in the lane that is attached near the tube of the cathode brings about blacking. Luminance output and luminous efficiency are decreased. So, it's necessary to replace it. if the user doesn't replace the lamp for a long time, it causes overvoltage in the lamp. Therefore, the filament might be overheated. Even the socket of the lamp might catch on fire. In this paper gives development model of the fluorescent lighting equipment which has ramp shift timely display device.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.525-535
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• 2009

In this paper a heuristic method for identifying individual pipes in water pipe networks to determine specific sections of the pipes that need to be replaced due to deterioration. An appropriate minimum pipe length is determined by selecting the pipe length that has the greatest variance of the average cumulative break number slopes among the various pipe lengths used. As a result, the minimum pipe length for the case study water network is determined as 4 m and a total of 39 individual pipe IDs are obtained. The economically optimal replacement times of the individual pipe IDs are estimated by using the threshold break rate of an individual pipe ID and the pipe break trends models for which the General Pipe Break Prediction Model(Park and Loganathan, 2002) that can incorporate the linear, exponential, and in-between of the linear and exponetial failure trends and the ROCOFs based on the modified time scale(Park et al., 2007) are used. The maximum log-likelihoods of the log-linear ROCOF and Weibull ROCOF estimated for the break data of a pipe are compared and the ROCOF that has a greater likelihood is selected for the pipe of interest. The effects of the social costs of a pipe break on the optimal replacement time are also discussed.

• Journal of Korea Water Resources Association
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• v.40 no.1 s.174
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• pp.39-50
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• 2007

This paper presents applications of the log-linear ROCOF(rate-of-occurrence-of-failure) and the Weibull ROCOF to model the failure rate of individual cast iron pipes in a water distribution system and provides a method of estimating the economically optimal replacement time of the pipes using the 'modified time-scale'. The performance of the two ROCOFs is examined using the maximized log-likelihood estimates of the ROCOFs for the two types of failure data: 'failure-time data' and 'failure-number data'. The optimal replacement time equations for the two models are developed by applying the 'modified time-scale' to ensure the numerical convergence of the estimated values of the model parameters. The methodology is applied to the case study water distribution cast iron pipes and it is found that the log-linear ROCOF has better modeling capability than the Weibull ROCOF when the 'failure-time data' is used. Furthermore, the 'failure-time data' is determined to be more appropriate for both ROCOFs compared to the 'failure-number data' in terms of the ROCOF modeling performances for the water mains under study, implying that recording each failure time results in better modeling of the failure rate than recording failure numbers in some time intervals.