• Korean Journal of Construction Engineering and Management
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• v.19 no.5
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• pp.3-9
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• 2018

Although Life Cycle Cost (LCC) must be evaluated by experts, sometimes it may not allow a sufficient time for even the experienced LCC expert to make rational decisions. Therefore, it often ends with relatively comparing the final numbers. We have broken down 110 technical proposals that are actually bade and accepted for large construction projects, and then have analyzed the uncertainty of Maintenance and Energy (M&E) cost during building life cycle, which turns out be the most volatile factor in uncertainty of LCC. Also we suggest "Value Engineering Index (VEI)" - the reduced M&E cost that is normalized by the reduced first cost. It is analyzed that the most uncertain factors of the M&E cost include repair and replacement term differing from each project, duplicated repair and replacement, non-standard repair items, and site-specific energy cost. Eventually we propose a VEI population with a mean of 1.38 and a standard deviation of 1.19, which is obtained by individually and exclusively applying the uncertain factors of the M&E cost to the 35 standard sample of technical proposals. The LCC evaluators may be able to use the VEI population as the benchmark to select the technical proposal with the most reasonable LCC among many others in two suggested manners; the one is to deterministically calculate the probability of single VEIs, and the other is to stochastically calculate the probability of the VEIs where uncertainty is quantified.

• Journal of the Korean Data and Information Science Society
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• v.27 no.6
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• pp.1557-1564
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• 2016

Recently, an extended warranty of a system following the expiration of the basic warranty is becoming increasingly popular to the user. In this respect, we suggest a two stage maintenance policy under the non-renewing warranty from the user's point of view in this paper. In the first stage, the user has to decide whether or not to purchase the extended warranty period. And, in the second stage, the optimal replacement period following the expiration of the warranty is determined. Under the extended warranty, the failed system is minimally repaired by the manufacturer at no cost to the user. We utilize the expected cost from the user's perspective to determine the optimal two stage maintenance policy. Finally, a few numerical examples are given for illustrative purpose.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.141-148
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• 2008

This study was conducted to evaluate the effect of PAC(Powder Activated Carbon) retention time on stable operation of high concentration powered activated carbon(HCPAC-MBR) in the treatment of secondary domestic wastewater. The pilot scale HCPAC-MBR system was operated at two different SRTs, 25 days and 100 days. The main drawback of HCPAC-MBR system was the rapid increase of trans-membrane pressure. The increase rate of trans-membrane pressure was proportional to SRT value at constant flux. This result seemed to be caused by reduced amount of EPS adsorbed on the PAC in the reactor by decreasing the SRT of the PAC. The particle size of the PAC was also influenced by SRT. The PAC size was decreased as SRT was increased. The change of particle size could be one reason for the change of trans-membrane pressure. The pore volume in the cake-layer formed on the membrane surface became to be increased by reducing SRT, because the cake-layer was highly composed of the PAC. Therefore, increased pore volume might play a role to reduce the trans-membrane pressure. The removal rate of E260 and TOC was also inversely proportional to SRT value.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.85-92
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• 2011

The role of RCDs(Residual Current Protective Device) that are installed before the load is very important for preventing electric shock and electrical fire. However, although fault rate of RCD is increasing due to deterioration and long period usage, the RCD is permanently used without a checking of performance evaluation and it causes the electrical accident. In this paper, the amount of airborne chloride is researched in domestic costal area and the accelerated life test is conducted using a salt water spray tester in order to decide the life time of RCD. Aa a result of an accelerated life test, the MTTF(Mean Time To Failure) of RCD is 110.81 hours and B10 life time of RCD is 45.81 hours for the all samples. when an accelerated life test result is applied to within 2 km costal area, the life time of RCD is predicted about 5 years.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.352-364
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• 2007

It is essential to reduce track maintenance costs and to extend the periodic replacements of continuous welded rails based on accumulated passing tonnage. As recently train load decrease and rail joints wear down less, the periodic replacements of continuous welded rails can be extended. There are many kinds of rail damage like squat, head-check and corrugation. These can be taken nondestructive or naked eye test. So the periodic replacements of continuous welded rails based on accumulated passing tonnage were examine with focusing on a crack of rail bottom of continuous welded rail. Therefore, this study measure dynamic response of track by metro train load, it compute impact coefficient and track spring coefficient for estimating a condition of actual track system. Also, it is converted the measured stress waveform into stress frequency histogram by the rain-flow counting methods, and then the equivalence of stress is calculated. As apply s-n curve of a new welded rail, accumulated fatigue damage ratio of laid rail and remaining service lives is estimated. This study suggest a plan of the periodic replacements of continuous welded rails based on accumulated passing tonnage classified by the types of track system.

• Journal of the Society of Disaster Information
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• v.12 no.4
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• pp.381-388
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• 2016

In this study, we surveyed the supply and perception of Personal Protective Equipments for firefighters. As a result, most of the respondents answered that they were paid in accordance with the supply standard, but 12% of the respondents said that there were insufficient equipment. Also, satisfaction with the performance of the equipment is mostly satisfied, but the safety gloves are more than 50% dissatisfied. In summing up the results of the survey, it is urgently necessary to improve the current supply standard, which is determined by the life of PPE, to the replacement period according to the using time or frequency. Also, a new standard should be prepared through the follow - up study.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.301-306
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• 2011

건축물의 다양한 설비는 내부 거주자의 안전, 쾌적, 위생 등 환경적 요구를 충족시켜주는 기능을 수행한다. 소방용 설비의 경우 화재발생시 인명과 재산피해를 최소화하기 위한 중요한 기능을 담당하며 평상시 자주 사용되지는 않지만 화재와 같은 사고 발생시엔 확실한 작동이 요구된다. 소방용 설비는 경년변화로 인한 기기의 성능저하 및 고장발생의 우려가 큼에도 그 특성으로 인해 고장 및 기기의 결함을 조기 발견하는 것이 어렵다. 이에 국내에서는 소방설비에 대한 점검 기준을 마련하여 이를 소방용 설비의 유지보수를 수행하고 있으나 형식적인 점검방법으로 인해 다음 점검주기까지의 성능보장이 불가능하다는 한계점을 가진다. 이러한 문제점을 개선하기 위해서는 공학적 근거에 의한 소방설비의 내구연한을 제시될 필요가 있어 국내에서도 현재까지 소방설비에 내구연한 산정에 관한 논의가 활발히 진행 중에 있으나 내구연한 산정방법과 기준에 대한 연구는 미비한 실정이다. 본 연구에서는 일본 공업회의 자주적인 대처로 산정된 소방용설비용 내구연한 사례를 분석 고찰하여 국내 소방설비 기기의 내구연한 및 교체시기 산정에 대한 기초연구를 진행하였다.

• Korean Journal of Digital Imaging in Medicine
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• v.17 no.1
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• pp.57-60
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• 2015

병원에서 사용되는 임상용 모니터의 관리는 중요하다. 모니터의 기본적 관리는 휘도이며, 휘도에서도 균일도가 가장 먼저 관리되는 대상이다. 특히 LCD 모니터인 경우 균일도에 문제가 모니터의 교체주기와 일치하는 경우가 많다. 휘도에 대한 평가는 여러 가지가 존재하지만, 본 연구에서는 AAPM TG18에 따라 TG18-UNL10, TG18-UNL80을 이용하여 휘도의 균일도를 조사하였다. 이 조사과정에서 측정값 중 가장 높은 수치를 기준으로 나머지 값의 편차를 구하는 방법과 평균값을 이용하여 측정값의 편차를 구하는 방법 두 가지를 사용하였으며, 두 가지 방법의 유의성을 알아보고자 휘도의 편차 변화량 즉, 균일도를 측정하였다. 휘도 균일도의 정량평가는 향후 모니터의 관리에 가장 큰 영향을 미치는 인자로써 측정기간 중 변화량은 매우 적게 나타났다. 따라서 본 연구에서 제시된 최대, 최소값의 편차나 평균값의 상대 편차값 모두 유의한 결과를 얻을 수 있었다.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.73-80
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• 2002

운영 자료의 조사$\cdot$분석을 위해 수도권 광역상수도의 취수장, 가압장 및 정수장들을 발문하여 각 펌프장에서 관리하고 있는 운전일보, 기기이력카드 등과 한국수자원공사에서 발간하는 월보 및 년보와 각 단계별 실시설계 보고서 및 준공도소를 수집하여 통계 처리한 결과를 요약하여 보면 다음과 같다. 각 단계별 수도권 광역상수도의 취수량 및 송수량은 운영을 시작한 초기부터 1990년까지 증가하다가 점점 수량이 감소하는 추세이다. 팔당 1 취수펌프장은 계획 취수량의 $95.5\%$, 2 취수펌프장은 $89.8\%$를 공급한 후 계속 감소되었고 설계 시 $100\%$의 용수량을 만족시키지 못하고 있다. 이러한 현상은 최근 IMF로 인하여 건설경기 둔화와 용수 수요량이 감소하였을뿐만 아니라 지방자치단체별로 취수펌프장을 독자적으로 건설하여 수요량 감소가 심화되었기 때문인 것으로 판단된다. 각 단계별 광역상수도 중 펌프의 운전토출압력과 운전흡입압력으로 부터 전양정을 계산하여 보면 설계된정격양정보다 낮은 수치인 저양정$\cdot$대유량으로 운전되고 있음을 알 수 있다. 이러한 운전은 캐비테이션을 발생시키고 이로 인하여 임펠러에 침식이나 균열이 발생하여 10년에 한번씩은 임페러를 교체한 것으로 나타났다. 그리고 펌프의 교체 주기는 $15\~20$년인 것으로 조사되었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.499-502
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• 2011

The advances in Information Technology have made examining the condition of vehicles possible with using various functions of a Smart Phone. Users have not realized the necessity of auto diagnosis system, for previous system required professional knowledge about vehicles. Because of this inconvenience, special system which is easy to use and quick to grasp its condition by smart phone is asked for users. In this research, auto diagnosis system is designed in Windows Phone. The replacement cycles for auto consumables, examining vehicle problems, and information of eco driving indicator are delivered in real time for auto drivers by using OBD-II information which is through wifi module in OBD-II protocol adaptor connector.