• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.802-809
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• 2021

To cope with the increasing maintenance costs due to aging, the maintenance cost was evaluated from the perspective of asset management. The maintenance cost can be predicted based on the condition of the bridge, and the life cycle cost is used as an index. In general, the condition of a bridge has a wide distribution characteristic depending on the deterioration, load, and material characteristics. In this paper, to evaluate the effect of the bridge conditions on the life cycle cost, condition prediction models were constructed considering the service life, deterioration rate, and inspection error, which are the main variables of the bridge condition and life cycle cost calculation. In addition, condition prediction models were constructed based on the distribution of the health index to estimate the upper and lower bounds of the life cycle costs that can occur in individual bridges. Life cycle cost analysis showed that the life cycle cost differed significantly according to the condition of the bridge. Accordingly, research will be needed to increase the reliability of predicting the life cycle cost of individual bridges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.25-33
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• 2012

In electric power transmission tower structures on offshore, implementation of life management using the event data of regular safety inspections for structural and material damages is strongly recommended. In this study, six tower structures in Sihwa Lake around Yeoungheung island were target bodies for the safety inspections. safety inspections for deterioration about each of six towers were performed about three items for steel member, five items for concrete foundation, and four items for steel-pipe pile in seawater and seawater itself. Safety inspections for steel members included the visual observations of surface appearances, the measurements of member thicknesses, and the checks of painting states. Also safety inspections for concrete foundations comprised the estimation of crack features, the evaluation of non-destructive compression strengths, and the measurements of neutralization depths and chlorides contents. For steel-pipe piles in seawater the inspections comprised the surveys of corrosion states in accordance with potential levels tests and anode tests, the analyses of photos taken on surfaces of the piles as well as the evaluation of seawater quality. A set of deterioration inspections was performed at the same positions around october of each year for three consecutive years. As a result in this study, Newly developed deterioration indexes have been applied profitably to maintain structural safety for electric power transmission towers by utilizing these event data systematically.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.85-91
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• 2021

Type 1 and type 2 buildings must regularly conduct precise safety inspections and precise safety diagnosis for the safety and maintenance of facilities, and the safety grade of the building is determined according to the results of the implementation. In addition, the cycle of inspection and diagnosis is determined according to the safety grade of the building. In order to determine the safety grade of the building, a precise safety inspection conducts condition evaluation, and a precise safety diagnosis conducts condition evaluation and safety evaluation. Therefore, since the inspection and diagnosis cycle is determined according to the safety grade of the building, the condition evaluation and safety evaluation must be precise. However, in the case of member unit evaluation, which is the first step in evaluating the current condition, the evaluation grade is determined by using the representative value of the measurement result, and this may result in an error in the evaluation grade. To solve this problem, this study analyzed evaluation criteria for each evaluation item and presented evaluation criteria using inequalities to respond to measurement results and evaluation scores. In addition, we present a functional formula that can reflect performance scores for each evaluation item.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.293-300
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• 2012

This study was to investigate the unsuitable rate of the storage facilities, the changes in corrosion process over time after installation according to the status, the time to install the facilities, years elapsed after facilities installation, inspection of methods and motivation, and so on, based on the results of the inspection at the petroleum storage facilities conducted by domestic soil-relate specialized agency to derive optimal management plans which meet the status of soil contamination facilities. The results showed that the facilities more than 5 years after the initial leak test at the time of the installation need to be inspected periodically by considering costs of leak test and remediation of polluted soil. The inspection period can be decided by cost and leak test methods showing discrepancies for the results obtained from individual test whether it was direct or indirect. To compensate these matters, we suggested that the direct inspection method on regular schedule is recommended. On the other hand, the inspection can be voluntarily completed to ease burden of the results by inspection or equivalent level to this inspection method. Also, it may need improved construction supervision and performance test system to minimize the occurrence of the nature defects in installing the facilities as well as the upgrade program for the facilities during intervals of inspection period.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.600-607
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• 2007

In this paper, we propose a MLKA (Multi-Level Keep-Alive) algorithm based on PRCG (Periodic In this paper, we propose a MLKA (Multi-Level Keep-Alive) algorithm based on PRCG (Periodic Ranging Code Group), in which periodic ranging codes are divided into groups. The AP (Access Point) performs this algorithm when a periodic ranging code arrives at the AP in a WiBro (Wireless Broadband Internet) system. In order to increase the traffic radio bandwidth resource efficiency in this system, we propose the multi-level keep-alive algorithm for finding abnormal AT (Access Terminal). From simulation results, it is verified our proposed MLKA algorithm based on PRCG can provide higher traffic radio resource efficiency compared to message-driven keep-alive algorithms.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.285-285
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• 2015

댐 및 저수지 시설물은 노후화나 안전성 미확보로 인한 파손 또는 붕괴 발생 시 하류부에 막대한 인명과 재산피해 등 치명적인 결과를 초래하게 된다. 이러한 대형 안전사고를 예방하고자 시설물의 안전관리에 관한 특별법에서는 댐 시설물을 규모별로 1, 2종 시설물로 구분하고, 이에 대해 주기적으로 안전점검 및 정밀안전진단을 실시하도록 제도화하는 한편 진단 결과에 따라 보수 보강 등의 안전조치를 의무화하고 있다. 구조물 결함에 따른 보수 보강은 보수재료와 공법 선정시 공법의 적용성, 구조적 안전성, 경제성 등을 종합적으로 검토하여 결정하여야 한다. 손상 부위에 대한 보수 보강은 제한된 예산과 인력을 효율적으로 투자하기 위해 보수재료 및 공법의 선정 뿐만 아니라 보수 보강이 이루어져야 하는 부재에 대한 우선순위를 산정하는 것이 최우선적으로 선행되어야 한다. 안전점검 및 정밀안전진단 세부지침에서는 보수 보강 대책 마련 시안전점검 및 정밀안전진단 결과를 기초로 하여 적정 재료 및 공법을 선정하고, 보수 보강의 수준 및 우선순위를 결정하도록 명시되어 있다. 하지만 우선순위 결정에 대한 가이드라인이 부재하여 불필요한 시공과 비효율적인 예산 투입으로 인해 국가예산의 낭비되고 시설물의 안전까지 위협받게 되는 경우가 발생하고 있다. 따라서 본 연구에서는 시설물의 상태에 따른 적절한 보수 보강 필요성을 판단하고 보수 보강 수준 및 우선순위를 결정하기 위한 방법론을 개발하였다. 댐 시설물에 대한 안전점검 및 정밀안전진단의 종합평가는 평가대상 개별시설에 대하여 상태 평가 및 안전성 평가를 실시한 후 그 결과에 의해 산출된 상태평가지수와 안전성평가지수를 비교하여 평가단계별로 그 결과를 취합하여 종합평가를 실시하고 있다. 따라서 상태평가에 의해 산정된 종합평가 결과를 이용하여 개별 부재의 상태평가값 산정을 위해 하부 단계의 가중치 및 평가 지수 역산하고, 재산정된 가중치 및 평가지수를 이용하여 각 부재에 대한 보수 보강 우선순위를 산정하고자 하였다. 개발된 방법론은 점검 진단 책임기술자 및 시설물 관리주체 담당자가 댐 시설물의 개별부재에 대한 보수 보강 실시 여부를 판정할 수 있는 기준으로, 보수 보강에 대한 정책 결정시 경제성을 고려한 신뢰도 있는 기준으로 활용될 수 있을 것으로 기대된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2191-2198
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• 2017

The PME(precision measurement equipment) used in the measurement to check the performance of the equipment in military weapon system is periodically calibrated to maintain measurement reliability during the life cycle. Previous studies suggest that reliability models are determined by considering sample size and characteristics of equipment. However, it may not be fit well to apply a single model assuming the same characteristic distribution for the maintenance date of many kinds of PMEs. This paper proposes that the most suitable calibration interval for maintenance data is selected through the F-test and the performance index evaluation among the calibration intervals estimated from the measurement reliability models assuming the characteristic of the bath-tub curve during the life cycle of various PMEs. The research results show that the reliabilities of various types of equipment are maintained during calibration intervals.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.7 no.3
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• pp.23-40
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• 1997

There are a lot of security tools for the investigation and improvement of UNIX systems. However, most of them fail to provide a consistent and usable user interface. In addition, they concentrate on a specific aspect of a system, not the whole one. For the overall management, system administrators cannot help using several uncomfortable tools. This paper introduces an integrated security analysis tool, named "Zkimi", which provides a convenient user interface and investigates the various aspects of UNIX systems such as account security, system security, network security, and file system integrity. The Zkimi supports user-friendly WWW based interface, so administrators can examine the various aspects of system more easily. We tried the tool for a system of a moderate size, and were confirmed that the tool is very efficient for investigating various security aspects of a system. a system.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1723-1728
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• 2009

수자원시설물의 유지관리와 조사, 계획, 설계, 제작, 설치, 운전, 보전을 거쳐 폐기에 이르는 시설물의 Life Cycle을 관리하기 위해 IT 기술을 이용하여 설비를 체계적으로 운영 관리하고 있다. 수자원시설의 점검관리에 있어 기존의 관리방법은 점검자가 관리항목을 대장에 기입하고 기입한 자료를 PC에 저장하여 관리함으로써, 업무의 복잡성 및 중복성이 발생됨으로써 업무효율이 저하되고 있는 실정이다. 이에 따라, 본 연구에서는 이러한 문제점을 효율적으로 해결하기 위하여 유비쿼터스 기술인 RFID를 현장에 적용하기 위하여 수자원시설에 대하여 표준코드를 정립하였으며, 수자원시설 이력관리 구축을 위하여 RFID 현장에 적용하고, RFID 리더기를 이용하여 시설물의 이력 관리 시스템과 연동하여 체계적인 시설관리 기반을 구축하였다. 이로써, 시스템을 통해 관리되는 시설물의 이력정보를 활용하여 설비 교체주기, 통계자료 조회, 예산 반영 계획수립 등의 업무에 즉시 적용이 가능하며 체계적이고 효율적인 업무수행이 가능할 것으로 판단된다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1177-1183
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• 2013

In this paper, the analysis of inspection period bases on reliability is suggested in the field of traction power system. Even though there are several maintenance models, the most commonly used maintenance assessment has been focused on time based maintenance in real traction power systems. The maintenance intervals are selected on the basis of long-time experience. It ensures high availability and exact planning of staff. Reliability centered maintenance, which evaluates criticality and severity of each failure mode, achieves the operation, maintenance, and cost-effective improvement that will manage the risks of equipment. This paper deals with electrification in railway inspection frequency and applied reliability based inspection frequency instead of constant intervals. The distribution function of failure rate in traction power system belongs to Weibull function. Also, the fault data and the number of installed equipments for electrifications are collected. The failure history is investigated and classified in detail. Though these complicated procedures, it contribute to extend equipment lifetime and to reduce maintenance costs.