• Title, Summary, Keyword: low-maintenance

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A Life Cycle Cost Model and Procedure for the Acquisition of Rolling Stocks (철도차량 획득을 위한 수명주기비용 모형 및 적용 절차)

  • Kim, Jong-Woon;Chung, Kwang-Woo;Park, Jun-Seo;Chung, Jong-Duk
    • Journal of the Korean Society for Railway
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    • v.13 no.3
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    • pp.257-263
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    • 2010
  • Operation and maintenance cost of a rolling stock is generally higher than its acquisition cost. Therefore, it is necessary for reducing life cycle cost (LCC) to make rolling stocks easy and low costly for operation and maintenance. In addition, their operation and maintenance support systems should be effective and efficient. To accomplish this, operator should specify LCC requirements in the early stage of acquisition and make a contractor to provide the rolling stocks of low LCC. This article presents a procedure and a verifiable LCC model available in the general acquisition process where an operator specify requirements and a contractor provide the rolling stock meeting the requirements.

Estimation of Performance and Pavement Life using National Highway Pavement Condition Index (NHPCI 지표를 활용한 공용성 추정과 수명 산정)

  • Do, Myung-Sik;Lee, Yong-Jun;Lim, Kwang-Su;Kwon, Soo-Ahn
    • International Journal of Highway Engineering
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    • v.14 no.5
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    • pp.11-19
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    • 2012
  • PURPOSES: The new methodology is proposed for estimation of long-term performance and pavement life based on the national highway database in Daejeon area. Furthermore, this study tried to verify the applicability of performance estimation using NHPCI (National Highway Pavement Condition Index) on tendency of pavement deterioration as time goes by under Korean road environments. METHODS: Reliability theories are applied to estimate the mean life and to determine the appropriate distribution using 3 levels of traffic loads (high, medium, low) based on maintenance and rehabilitation history data for 15 years. RESULTS: As a result, Lognormal distribution is suitable for explanation of pavement lifetime in Daejeon area regardless of traffic loads. In addition, we found that the results of mean life and maintenance timing based on NHPCI for the pavement sections of 3 levels of traffic loads are available. CONCLUSIONS: Based on this study, it was found that mean life of high, medium and low levels of traffic loads are about 8.1 years, 12.2 years and 12.7 years, respectively. Higher level of traffic loads shorten the pavement mean life.

Fuel-Optimal Altitude Maintenance of Low-Earth-Orbit Spacecrafts by Combined Direct/Indirect Optimization

  • Kim, Kyung-Ha;Park, Chandeok;Park, Sang-Young
    • Journal of Astronomy and Space Sciences
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    • v.32 no.4
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    • pp.379-386
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    • 2015
  • This work presents fuel-optimal altitude maintenance of Low-Earth-Orbit (LEO) spacecrafts experiencing non-negligible air drag and J2 perturbation. A pseudospectral (direct) method is first applied to roughly estimate an optimal fuel consumption strategy, which is employed as an initial guess to precisely determine itself. Based on the physical specifications of KOrea Multi-Purpose SATellite-2 (KOMPSAT-2), a Korean artificial satellite, numerical simulations show that a satellite ascends with full thrust at the early stage of the maneuver period and then descends with null thrust. While the thrust profile is presumably bang-off, it is difficult to precisely determine the switching time by using a pseudospectral method only. This is expected, since the optimal switching epoch does not coincide with one of the collocation points prescribed by the pseudospectral method, in general. As an attempt to precisely determine the switching time and the associated optimal thrust history, a shooting (indirect) method is then employed with the initial guess being obtained through the pseudospectral method. This hybrid process allows the determination of the optimal fuel consumption for LEO spacecrafts and their thrust profiles efficiently and precisely.

Review on predictors of dropout and weight loss maintenance in weight loss interventions (비만치료에 있어서 중도탈락과 감량 후 체중유지에 영향을 주는 인자들에 대한 고찰)

  • Kim, Seo-Young;Park, Young-Jae;Park, Young-Bae
    • The Journal of Korean Medicine
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    • v.37 no.3
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    • pp.62-73
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    • 2016
  • Objectives: Dropout and weight regain are common problems in most obesity treatments. The purpose of this study was to review previously published study results of the predictive factors associated with dropout during weight loss treatment and weight loss maintenance after successful weight loss. Methods: Authors searched for the articles related to dropout and weight loss maintenance, published from 2007 to 2016 found on Pubmed, Scopus, RISS, and KISS. A total of 19 articles were finally selected. From the study results, unchangeable and changeable predictors were extracted, and these predictors were examined according to dropout and weight loss maintenance categories. Results: The unchangeable predictors of dropout were younger age, lower education level and female, whereas the changeable predictors of dropout were lower initial weight loss, symptoms of depression and body dissatisfaction. The strongest factor for predicting the dropout was initial weight loss. The unchangeable predictors of weight loss maintenance were old age, male and family history of obesity, whereas the changeable predictors of weight loss maintenance were regular exercise, dietary restraint, self-weighing and low depressive symptoms. Initial weight loss, depressive symptoms, body image, dietary restraint, physical activity, weight loss expectation and social support were considered to be dominant factors for weight loss treatments. Conclusions: Our review results suggest that unchangeable and changeable predictors of dropout and weight loss maintenance should be carefully examined during treatments of obesity.

A Study on the Development of Waste-Water Maintenance Management System Using GIS (GIS를 활용한 하수도 유지관리시스템 개발에 관한 연구)

  • Kim, Ki-Woo;Cho, Sung-Eon
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.11-14
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    • 2001
  • This paper is studied on waste water maintenance management system for Integrated computing environment. This computing environment consist of Waste-Water Maintenance Management and GIS(Geographic Information System). This system can be developed by constructing Database which is set of rules occurring while management work of waste water system is processed. This system will help person who has responsible for making decision. Objective of such computing environment is providing efficient working environment for waste water facility management. Especially we analyzed problems of existing waste water maintenance management. We carried out efficient management of water facility and it will provide solution for major decision making work with low cost using Waste-Water Maintenance Management System

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Maintenance Crude Protein Requirement of Penned Female Korean Spotted Deer (Cervus nippon)

  • Yang, S.Y.;Oh, Y.K.;Ahn, H.S.;Kwak, W.S.
    • Asian-Australasian Journal of Animal Sciences
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    • v.27 no.1
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    • pp.30-35
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    • 2014
  • This study was conducted to evaluate the protein requirement for maintenance of 2-year-old female Korean spotted deer. In the course of the experiment, each of three hand-reared female spotted deer was fed three diets that were iso-calorically formulated to contain low (approximately 7%), medium (12%), and high (17%) levels of crude protein (CP). Each of six trials included a 5-day transition, a 10-day preliminary, and a 7-day collection period. Dietary protein levels affected the apparent digestibility of CP (p<0.05) but not the apparent digestibility of dry matter, organic matter, or acid detergent fiber. All of the deer showed a positive CP balance on all of the diets. The maintenance CP requirement estimated by regression analysis was 4.17 g/kg metabolic body weight $(W^{0.75}){\cdot}d$. The maintenance digestible CP requirement was 1.42 g/kg $W^{0.75}{\cdot}d$. The metabolic fecal CP was 1.95 g/kg $W^{0.75}{\cdot}d$. The blood urea nitrogen of spotted deer increased (p<0.05) as the dietary protein levels increased.

The Application Analysis of Power System Stabilizer in Hydraulic power plant (전력계통안정화장치(PSS) 수력발전소 적용분석)

  • Ok, Yeon-Ho;Lim, Jae-Il;Park, Ji-Kun;Kwak, Won-Ku;Lee, Kwang-Yeon
    • Proceedings of the KIEE Conference
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    • pp.63-65
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    • 2007
  • Recently with increase consumption of electric power, the scale of the electric system becomes bigger and complex. Then, it is increasing the hardship in the operation of electric system and the continuance of stability. Especially, as the differences between demand and supply in electric power keeping low frequency oscillating attenuation from electric power have been very important in the continuance part of stability. The more control time of electricity system is getting faster with digitalization the more stability of electricity system is getting worse. As solutions of these problems, by establishing Power System Stabilizing Controller putting PSS output signal and putting damping to vibration of the rotor at generators's AVR in area where is oscillated, We are willing to contribute the electricity system by holding in generator output vibration.

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A study on the electric locomotive maintenance (신형전기기관차 유지보수에 관한 연구)

  • Yu, Yang-Ha
    • Proceedings of the KSR Conference
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    • pp.765-771
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    • 2008
  • After the KTX operation Korail has been making great effort to reliability settlement through RCM. Also maintenance cycle and method optimization for normal speed rolling stock field are lively same as high-speed rolling stock. In this paper maintenance techniques for new model electric locomotive are introduced. To find the optimal maintenance method, locomotive inspection cycle for advanced country are examined and other electric locomotive inspection cycle are compared. As a result the present time inspection cycle is totally focusing on safety aspect so the economical efficiency is quite low. Through this research optimal maintenance technique will be accomplished in the end of year 2008.

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Non-contact Impact-Echo Based Detection of Damages in Concrete Slabs Using Low Cost Air Pressure Sensors (저비용 음압센서를 이용한 콘크리트 구조물에서의 비접촉 Impact-Echo 기반 손상 탐지)

  • Kim, Jeong-Su;Lee, Chang Joon;Shin, Sung Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.3
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    • pp.171-177
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    • 2011
  • The feasibility of using low cost, unpowered, unshielded dynamic microphones is investigated for cost effective contactless sensing of impact-echo signals in concrete structures. Impact-echo tests on a delaminated concrete slab specimen were conducted and the results were used to assess the damage detection capability of the low cost system. Results showed that the dynamic microphone successfully captured impact-echo signals with a contactless manner and the delaminations in concrete structures were clearly detected as good as expensive high-end air pressure sensor based non-contact impact-echo testing.

Field Application of Low Heat Concrete Using Strontium Hydroxide Based Latent Heat Material (스트론튬계 잠열재를 사용한 저발열 콘크리트의 현장적용 평가)

  • Khil, Bae Su;Yun, Hyun Do;Jeong, Ok Ran
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.5
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    • pp.218-226
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    • 2011
  • Low heat concrete using strontium hydroxide based latent heat material was manufactured in ready-mixed concrete batcher plant and its fundamental properties were tested. As a result of B/P test, its applicability to the construction site was verified. After B/P test, low heat concrete using strontium hydroxide based latent heat material was applied to the real construction site of bridge footing. Through the analysis and the actual measurement of the hydration heat of the concrete footing, the reduction effect of hydration heat and thermal crack was confirmed.