• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.409-412
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• 2006

펀드의 성과 평가는 펀드선택 의사결정시 가장 중요한 고려요인이다. 전통적인 펀드 성과평과 지표인 샤프비율이나 트레이너 비율은 운용비용과 거래비용 등과 같은 다양한 요소들을 반영하지 못하고 있다. 펀드의 여러 수익과 비용요인들을 반영하기 위해, 본 연구에서는 DEA를 이용하여 펀드의 상대적인 효율성을 측정하였다. 분석자료는 2005년 12월 31일까지 국내에 존재하는 3년 이상 운용된 67개의 장기펀드를 대상으로 분석하였다. 입력변수는 비용과 관련된 총 보수율, 월수익률의 표준편차, 펀드 규모를 나타내기 위한 평균설정좌수를 이용하였고 출력변수는 이익과 관련된 예상 월평균수익률과 시장포트폴리오의 월수익률을 상회한 기간의 비율을 사용하였다. 본 연구결과, DEA를 통해 수익률만으로는 평가할 수 없는 펀드의 운용능력을 평가할 수 있었다.

• Journal of the Korean Society for Railway
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• v.15 no.4
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• pp.381-387
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• 2012

This paper is aimed to analyze the achievements of the Tunnel Monitoring System(TMS), implemented in Seoul subway L5~L8, and to find out improved methods. By introducing the TMS, it is possible to inspect tunnel facilities for 24 hours a day while trains are operated. The inspection capability could be expanded, the accuracy was improved, and the cycle was shortened. The efficiency of manpower was improved and the surplus manpower could be used for other tasks of facilities maintenance. As a result, by introduction of the TMS, the amount of tunnel maintenance was increased by 225% and the train service troubles caused by facility problems were decreased by 53%.

• KDI Journal of Economic Policy
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• v.33 no.1
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• pp.45-72
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• 2011

This study uses Korea's equity fund-related data ranging from Jan. 2002 to Apr. 2010 to analyze the existence of cross-subsidization among funds managed by the same management company. The findings are as follows: i) a transfer of performance outcome is confirmed to move from low-fee funds to high-fee funds, meaning that management companies tend to maximize their own interest than investors' return. And such a tendency has been strengthened since 2008. ii) young funds overperform old funds, iii) funds with high returns in the previous quarter perform better than funds with low return in the same period. These results suggest that in order to protect investors, it is necessary to conduct close monitoring on transactions that might undermine the benefits of investors and comprehensive evaluation on the capability of management companies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.130-137
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• 2017

To maintain traffic safety during the target lifetime of bridges, it is essential to secure an appropriate maintenance budget and allocate that budget appropriately. This paper proposes a reasonable budget allocation system that considers various impact factors to improve the conventional budget allocation method simply considering the bridge scale. The maintenance action rate model and the unit cost model based on the prior maintenance history were developed to allocate appropriately the bridge maintenance budget for the total bridges of the management organization with the target management level. A method to determine the optimal budget allocation ratio for each management subject was proposed and case analysis was conducted using the proposed model. Proper budget allocation was made considering the bridge types, current safety level, and service life as well as the bridge size as an impact factor of the budget allocation of the bridge. The developed method can prevent budget waste and provide a rational basis for budget allocation by implementing the rational budget distribution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.19-25
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• 2016

Engineering structures including civil infrastructures require a life-cycle cost and benefit during their service lives. The service life of a structure can be extended through appropriate inspection and maintenance actions. In general, this service life extension requires more life-cycle cost and cumulative benefit. For this reason, structure managers need to make a rational decision regarding the service life management considering both the cost and benefit simultaneously. In this paper, the probabilistic decision tool to determine the optimal service life based on cost-benefit analysis is presented. This decision tool requires an estimation of the time-dependent effective cost-benefit under uncertainty to formulate the optimization problem. The effective cost-benefit is expressed by the difference between the cumulative benefit and life-cycle cost of a deteriorating structure over time. The objective of the optimization problem is maximizing the effective cost-benefit, and the associated solutions are the optimal service life and maintenance interventions. The decision tool presented in this paper can be applied to any deteriorating engineering structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.288-295
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• 2011

The objective of this study is to develop a proper absorbent-pervious pavement. By using single graded aggregates and SAP, permeability and water absorbability of absorbent-pervious pavement are improved, and also temperature reducing effect is found out. And several tests such as compressive and flexural strength tests, and permeability/water absorption tests of absorbent-pervious pavement are carried out to verify these kind of effects. The compressive and flexural strengths are increased according to decrease of single graded aggregate size, and increase of SAP content. And the volume of water retention and absorbability are increased according to the increase of SAP content and these are also increased in small size of single graded aggregate. And about $20^{\circ}C$ of difference is observed in surface temperature between normal asphalt pavement and absorbent-pervious pavement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.77-86
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• 2007

The repair technique utilizing surface impregnant is widely used due to its simple construction procedures and economical benefit. Surface protection through this reparing technique cannot increase the bearing capacity of concrete members much but increase the durability performance and service life efficiently. In this study, fundamental tests such as water suction and permeation are performed for concrete specimens with several organic/inorgarnic impregnant and suitable impregnant is selected on the basis of the results. Finally, durability tests such as carbonation, freezing and thawing, and chloride attack are carried out for the concrete specimens with selected impregnant and it is experimentally verified that they have good resistance to deteriorations.

• Journal of the Korea Society of Computer and Information
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• v.24 no.11
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• pp.219-228
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• 2019

Naval command and control system are very important for operation and their failures can be fatal for warfare. To prepare for these failures, we use feature selection method which is one of the data mining techniques. First, we analyzes failure data set of Navy from 2016 to 2018. And then We derive attributes that are associated with failure and to predict failure using feature selection method. We propose a method for prioritizing maintenance using the degree of association of attributes. This improves the efficiency and economics of command and control system maintenance.

• Journal of Internet of Things and Convergence
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• v.8 no.6
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• pp.55-63
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• 2022

In recent years, with the rapid development of large and medium-sized urban rail transit in China, the total operating mileage of high-speed railway and the total number of EMUs(Electric Multiple Units) are rising. The system complexity of high-speed EMU is constantly increasing, which puts forward higher requirements for the safety of equipment and the efficiency of maintenance.At present, the maintenance mode of high-speed EMU in China still adopts the post maintenance method based on planned maintenance and fault maintenance, which leads to insufficient or excessive maintenance, reduces the efficiency of equipment fault handling, and increases the maintenance cost. Based on the intelligent operation and maintenance technology of PHM(prognostics and health management). This thesis builds an integrated PHM platform of "vehicle system-communication system-ground system" by integrating multi-source heterogeneous data of different scenarios of high-speed EMU, and combines the equipment fault mechanism with artificial intelligence algorithms to build a fault prediction model for traction motors of high-speed EMU.Reliable fault prediction and accurate maintenance shall be carried out in advance to ensure safe and efficient operation of high-speed EMU.

• Journal of Intelligence and Information Systems
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• v.29 no.3
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• pp.79-101
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• 2023

The current status of local road pavement management in Jeollabuk-do only relies on the accomplishments of the site construction company's pavement repair and is only managed through Microsoft Excel and word documents. Furthermore, the budget is irregular each year. Accordingly, a systematic maintenance plan for local roads is necessary. In this paper, data related to road damage and road environment were collected and processed to derive possible areas which could suffer from road damage. The effectiveness of the methodology was reviewed through the on-site inspection of the area. According to the Ministry of Land, Infrastructure and Transport, in 2018, the number of damages on general national roads were about 47,000. In 2019, it reached around 38,000. Furthermore, the number of lawsuits regarding the road damages were about 93 in 2018 and it increased to 119 in 2019. In the case of national roads, the number of damages decreased compared to 2018 due to pavement repairs. To measure the priorities in maintenance of local roads at Jeollabuk-do, data on maintenance history, local port hole occurrence site, overlapping business section, and emergency maintenance section were transformed into data. Eventually, it led to improvements in maintenance of local roads. Furthermore, spatial data were constructed using various current status data related to roads, and finally the data was processed into a new form that could be utilized in machine learning and predictions. Using the spatial data, areas requiring maintenance on pavement were predicted and the results were used to establish new budgets and policies on road management.