• Current Industrial and Technological Trends in Aerospace
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• v.8 no.1
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• pp.77-85
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• 2010

The current GPS constellation consists of 32 Block IIA/IIR/IIR-M satellites including 12 Block IIA satellites on service over 15 years. The satellites in poor space conditions may suffer from anomalies, especially influenced by aging atomic clocks which are of importance positioning and timing. Recently, the IGS Ultra-rapid predicted products have not shown acceptably high quality prediction performance because the Block IIA cesium clocks may be easily affected by various factors such as temperature and environment. The anomalies of aging clocks involve lower performance of positioning in the GPS applications. We, thus, describe satellite clock behaviors and anomalies induced by aging clocks and their detection technologies to avoid such anomalies.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.204-204
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• 2023

2020년 상수도 통계에 따르면 전국 상수도 보급률은 약 99% 정도로 높은 수치를 기록하고 있으나 노후관으로 인한 관로파손 및 수질사고로 인해 효과적인 운영에는 많은 어려움이 존재한다. 이러한 문제를 해결하기 위해 기술진단 및 정밀안전진단 등 체계적인 유지관리 규정이 도입되었으며 적용되고 있으며, 이때 시스템의 정량적인 성능평가를 위해 간접평가와 직접평가로 구성된 점수평가법이 적용되었다. 간접평가는 지중에 매설된 관로를 대상으로 매설연도, 관경, 관로연장 등의 노후도인자를 통해 관의 노후도를 추정하고 간접평가 결과 3등급으로 판명되는 관로의 경우 객관적인 관의 상태를 평가하기 위해 시편채취 및 관로 내시진단 등의 직접평가가 수행된다. 하지만 관로의 직접평가는 간접평가결과 3등급의 모든 관로에 대해 수행하기에는 진단비용 및 시간 등 제약조건에 따라 모든 지점에 대한 직접평가 수행에는 한계가 있다. 따라서, 본 연구에서는 이러한 관로 성능평가 기법의 한계를 개선하기 위해 상수도시스템 통합평가 기술을 개발하였다. 개발한 기술은 머신러닝 기법을 적용하여 간접평가 및 직접평가 결과를 토대로 직접평가가 필요한 지점의 결과를 예측하였다. 이를 바탕으로 상수도시스템 평가성능 향상 및 보강 우선순위 선정 단계에서 의사결정권자의 판단에 도움이 될 것으로 판단된다.

• 한국노년학
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• v.39 no.3
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• pp.569-587
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• 2019

This study aims to look at the factors affecting later-life expectation of semi-older adults. Total of 323 participants aged from 50 to 64 was used for analysis from the data of 'Korean's Perception on Aging Society', which was conducted on behalf of Initiative for Humanities' Research and Education, funded by National Research Foundation of Korea. Multiple regression analysis was used for analysis, and the results are as follows. First, later-life expectation of semi-older adults appeared to be high. Second, the significant factors were prejudice towards the elderly and social solidarity. That is, participants with lower prejudice towards the elderly and higher trust and solidarity with society showed greater later-life expectation. Based on the results of this study, future research directions and implications for policy and practice were suggested.

• Korean Journal of Construction Engineering and Management
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• v.13 no.6
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• pp.13-23
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• 2012

While Category 1 and Category 2 bridges are intensively inspected and carefully managed, many small bridges that are not in the Category 1 and 2 are often forgotten until they decay in serious condition. Since many of these small bridges located in the populated city, failure of them would cause huge negative impact on the community. This paper focuses on the small size concrete bridges for timely repair and rehabilitation work for the effective operation and management. Test bed is developed to define the key parameters to forecast the long term performance of the bridges, mostly concrete box bridges. Key parameters suggested in this paper are cumulative fatigue due to repetitive heavy traffic loads and the acid attacks for concrete material deterioration. The cumulative fatigue is measured by the use of the mileage concept. For the long term data collection and inspection, stable and easy to use data collection system is installed as a test bed. The contribution of this research work is on the development of the test bed to define the key parameters of bridge deterioration.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.535-541
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• 2009

The reliability of control system composed of electronic parts has been studied by DoD since 1960, and has been undertaken mainly by Europe for railways. Especially in Korea, a study on reliability of signalling equipment has been taken since 2000, requiring reliability test for effective maintenance of old type signalling equipment which no longer has information on its past reliability. This study evaluates the reliability test in units of parts for old type signalling equipment; for instance, failure rate in units of parts, or failure data during operation; which was utilized without its consistent reliability monitoring and analysis data for over 20 years. Also, reliability change at this point in time has been estimated by using residual life span function, and a model which can evaluate the possibility of extended operation through stress acceleration test has been developed. This model will be utilized to establish future maintenance policy for train operating company's operation on old type signalling equipment.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.697-703
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• 2023

In this study, a modified indirect evaluation method was developed to predict the deterioration level of water pipes. The accuracy of the modified method was verified by comparing it with the direct method. The weights of index were adjusted by reducing the weight of water quality corrosion, soil corrosion, lay depth and road type according to the importance of the existing evaluation factors and adding the weight of pipe thickness. In the results, the weight of pipe thickness was determined to be 0.1530. Comparing with the direct evaluation method, the accuracy of the modified indirect evaluation method increased by 31.03% compared to the indirect evaluation method. The modified indirect evaluation method will be able to select relatively old pipes more accurately and efficiently than the existing indirect evaluation method when prioritizing the improvement of old water pipes.

• The Journal of the Korea Contents Association
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• v.16 no.9
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• pp.66-77
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• 2016

This research defined causal relationships among the perception of retirement and senior life(PRSL), retirement preparation actions(RPA), and retirement satisfaction level(RSL) to know the expectation about retired life according to the differences of retirement related factors, PRSL, and RPA. For this, From November 2015 to February 2016, I researched from 20 to 69, 1,500 currently working adults in the country, mailing surveys with the letter introducing this research's purpose and procedure and having them send them back, or researcher's spreading and collecting the surveys, eliminating 83 cases of negligent answers, finally analyzing 1,417 surveys. The result shows age, monthly income, and residing at their own places made more positive PRSL, RPA, financial retirement preparation level(FRPL), and expectancy about satisfactory retirement life. When they had less children, PRSL and RSL were higher. When they had more children, RPA was more proactive, and FRPL was higher. When they had positive PRSL, RPA was more proactive, and expectancy about retired life was higher. This research is significant in defining differences of retirement related factors and causal relationships among PRSL, RPA, and RSL.

• Korean Journal of Social Welfare
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• v.58 no.3
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• pp.313-340
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• 2006

The purpose of this study was to examine predictors of move intention to silver town in Jeju Island. Participants were 449 middle age and elderly who live in Seoul, Gyungido, Inchun Metropolitan and Jeju island. Participants were completed a questionnaire and/or structured interview that included measures of socioeconomic variables, motivation to move, determinants of move selection, conditions of location, and preparation for old age. Results of descriptive analysis revealed that cognition level of sliver industry and silver town was relatively high and medical service was the best necessary field, followed by field of leisure activity, house, life and finance. Logistic regression analyses on the effects of socioeconomic variables on move intention indicated that region, occupation and house ownership had significant effects on move intention to silver town. Result of motivational effect on move intention revealed that solution of offspring's burden was the most important factor, followed by convenient life of the aged, enjoyment of freedom for the elderly life. Result on the influence of determinants of move selection indicated that medical service facilities, resort facilities and leisure, cultural service facilities had significant effect on move intention. Among conditions of location for Jeju island, mild climate, comfort environment and low-price were significant predictors on move intention. Overall, result on relative influence of individual factors indicated that low price factor was the most important predictor, followed by resort facilities, cognition on necessity of silver town, enjoyment of freedom for the elderly life, leisure cultural service facilities, and medical service facilities.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.155-165
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• 2016

Pipe Deterioration Prediction (PDP) and Pipe Failure Risk Prediction (PFRP) models were developed in an attempt to predict the deterioration and failure risk in water mains using fuzzy technique and the markov process. These two models were used to determine the priority in repair and replacement, by predicting the deterioration degree, deterioration rate, failure possibility and remaining life in a study sample comprising 32 water mains. From an analysis approach based on conservative risk with a medium policy risk, the remaining life for 30 of the 32 water mains was less than 5 years for 2 mains (7%), 5-10 years for 8 (27%), 10-15 years for 7 (23%), 15-20 years for 5 (17%), 20-25 years for 5 (17%), and 25 years or more for 2 (7%).

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.349_350
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• 2009

가스개폐기의 고장을 예방하기 위해서는 열화상태를 진단하여 고장을 일으키기 전에 교체하는 것이 가장 바람직하다. 이를 위해서는 제품의 제조상태, 불량가능성 등 이력사항을 진단하고 활선 진단을 통한 내부 상태를 파악한 후 위험도를 평가할 필요가 있다. 본 연구에서는 국내 배전개폐기의 열화 및 수명인자를 이용하여 개폐기 고장 위험을 예측할 수 있는 기법을 제시하였다.