• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.349-358
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• 2019

This paper aimed at collecting sensor signals to extract characteristic parameter of the rotor. A vibration test rig has been developed to perform model tests. Signal characteristics were analyzed when driving normally. Envelope FFT Analysis is used to extract vibration components caused by periodic impacts from other vibration factors. Signal analysis was performed when load changes were given to speed sensors and vibration test rigs that show low frequency characteristics of the rotor and signal analysis according to rotational speed. The acceleration signal measured in the bearing housing has a small amplitude and produces only the rotational frequency component and harmonic component of the motor. As the number of rotations increases, the amplitude of acceleration can be seen. As the rotational speed increases, it can be seen that there is a difference in the shape of the original data and compared with the acceleration FFT graph, it can be seen that the noise is strong at low frequencies and the corresponding rotational frequency components are clearly represented. It can be seen that changing the load does not increase the main rotational frequency component.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.64-73
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• 2019

This study analyzed the efficiency by using the DEA model to evaluate the competitiveness of specialty construction firms. The target of the analysis is 300 firms with continuous data from 2010 to 2017 as listed and externally listed firms. Significant analysis results are as follows. First, the efficiency of specialty construction firms is lower than that of general construction industry. Second, efficiency by type was highest in facilities construction and dismantling work. This shows that the relevant industries such as reinforced concrete works and scaffolding and demolition work are relatively efficient in specialty construction industry. Third, the efficiency of specialty construction industry is affected by economic fluctuations. When the construction industry is in the expansion phase, the efficiency value is high and the efficiency value is low in the down phase. Finally, in the scale profitability analysis, specialty construction industry was most analyzed by DRS. This means that it is effective to scale down for the efficiency of the firm.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.3003-3014
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• 2018

This paper investigates whether the value relevance of unbilled revenue in the construction company is differentiated according to the degree of company's operational efficiency. Unbilled revenue is an item that appears in the assets of the statement of financial position based on the IFRS. It is an item that has a nature of accounts receivable, but it is calculated based on subjective judgment of management. In this paper, we hypothesized that the value relevance of unbilled revenue will be differentiated according to operational efficiency of the construction company. The results of hypothesis test are as follows. First, unbilled revenue has a significant relationship with firm's value, which is consistent with previous research results. Second, the value relevance of unbilled revenue is higher in companies with high operational efficiency. In conclusion, this paper is different from previous researches in that this paper presents not only that unbilled revenue has a value relevance but also provides evidence that it can be differentiated according to the degree of operational efficiency.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.2
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• pp.121-133
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• 2021

This study set up the estimates of leakage management efficiency evaluation and leakage management goal that could be used in local water distribution networks efficiency business and modernization business. The data were analyzed using data envelopment analysis and multiple regression analysis. To this end, with leakage management input indices concerning leakage reduction activities (e.g., aged pipe replacement, water meter replacement, leakage restoration, and leakage detection) and leakage management calculation indices (e.g., the increase of revenue water ratio and the reduction of leakage ratio), the data on 22 K-water consignment local water supply systems were analyzed for the years from 2004 through 2018. Using the results of efficiency analysis by data envelopment analysis, the other DMUs (Decision Making Unit) benchmarked the DMU with the highest efficiency to maximize the leakage management efficiency for all DMUs. Through this, leakage management goal estimates were drawn with the input indices of four leakage reduction activities and calculation indices of the increase of revenue water ratio and the reduction of leakage ratio by multiple regression analysis for each group based on the revenue water ratio and leakage ratio. The correlation coefficients of the leakage management goal estimate for the criteria for the revenue water ratio amounted to 0.553 and 0.771. The correlation coefficients of the leakage management goal estimate for the criteria for leakage ratio were 0.397 and 0.865. Accordingly, we estimated the quantity and priority of four leakage reduction activities for the target leakage ratio and revenue water ratio.

• The Journal of the Korea Contents Association
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• v.21 no.10
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• pp.309-321
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• 2021

While total sales of broadcasting business have been increasing, terrestrial broadcasters' sales are stagnant and comprehensive programming program providers(PPs)' sales are increasing. The purpose of this study is to derive implications by analyzing the relative efficiency and super-efficiency of domestic broadcasters in such an asymmetric situation. In this study, we use input and output data of three central terrestrial broadcasters and four comprehensive programming PPs from 2012 to 2019. For the analysis, Additive DEA model and Additive super-efficiency DEA model are used with the assumption of VRS condition since the broadcasting industry is characterized by economies of scale. As a result, we find out that the input excess of tangible assets is the most decisive cause of inefficiency that reduces the efficiency of central terrestrial broadcasters. On the other hand, for the comprehensive programming PPs, the input excess of tangible assets and the output shortfall of total sales are important factors of inefficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.50-59
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• 2021

The defense venture support program supports development so that it can be applied to the defense sector based on their technology and ideas to revitalize the private advancement of small and medium-sized enterprises to the defense sector. Since 2015, it has been operated with contributions from the Defense Acquisition Program Administration and has supported 84 projects. Moreover, it is an early stage in which results have been derived after 2018. In this study, the R&BD efficiency derived according to the budget for each project was compared using data envelopment analysis and classified and analyzed according to the characteristics of each project to identify the performance factors for each outstanding project. Based on the analysis results, this study considered support plans for efficient support programs and continuous performance creation in the future. As a result, it is expected that the effectiveness of the defense venture support project will be strengthened, and excellent performance will be expanded based on this study.

• The Journal of Society for e-Business Studies
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• v.26 no.2
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• pp.45-59
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• 2021

As software(SW) has been considered as a key driver of the fourth industrial revolution, significant R&D investment has been made by Korean government. Despite the attention and support by the government, systematic analysis on the SW R&D efficiency has not been fully addressed. In this study, the efficiency of SW national research and development projects was analyzed using Data Envelopment Analysis(DEA) techniques. Efficiency was measured from both static and dynamic perspectives based on 1,463 projects conducted by the National IT Industry Promotion Agency(NIPA) from 2008 to 2018. The static efficiency analysis identified the causes of inefficiency as scale and technology problems. As a result of dynamic efficiency analysis, we present a sector-specific response model using an efficiency-stability matrix. This study is meaningful in that efficiency analysis was conducted on the entire SW national R&D project, and static/dynamic efficiency analysis results are expected to be used as a guideline for planning SW national R&D project.

• International Area Studies Review
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• v.12 no.2
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• pp.79-97
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• 2008

After entering into the WTO in October, 2001, China started opening her bank industry on a full scale and her financial markets from the end of 2006. It is true that the Chinese commercial banks should make efforts to enhance their operational efficiency for adapting the rapid change of financial environments. In this paper, the efficiency of 4 Chinese state-owned commercial banks and 11 share holding commercial banks has been estimated. Our Tobit model to find out the determinants of these banks' efficiency. The results are as follows: The efficiency of these banks kept being improved from 1999 to 2003. With regard to the relationship between the determinants and the bank efficiency, their capital ratios, ownership structures and government subsidies are significant at the 5% level while the return on asset(ROA) is significant at the 10% level. The relationship between the determinants and the efficiency has showed that the size, capital ratios, ROA and ownership structure showed significantly before the entry to WTO, on the other hand, after WTO their capital ratios are the only factor to determine their efficiencies.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.2
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• pp.1-14
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• 2021

It is highly challenging to measure the efficiency of electric vehicle charging stations (EVCSs) because factors affecting operational characteristics of EVCSs are time-varying in practice. For the efficiency measurement, environmental factors around the EVCSs can be considered because such factors affect charging behaviors of electric vehicle drivers, resulting in variations of accessibility and attractiveness for the EVCSs. Considering dynamics of the factors, this paper examines the technical efficiency of 622 electric vehicle charging stations in Seoul using data envelopment analysis (DEA). The DEA is formulated as a multi-period output-oriented constant return to scale model. Five inputs including floating population, number of nearby EVCSs, average distance of nearby EVCSs, traffic volume and traffic congestion are considered and the charging frequency of EVCSs is used as the output. The result of efficiency measurement shows that not many EVCSs has most of charging demand at certain periods of time, while the others are facing with anemic charging demand. Tobit regression analyses show that the traffic congestion negatively affects the efficiency of EVCSs, while the traffic volume and the number of nearby EVCSs are positive factors improving the efficiency around EVCSs. We draw some notable characteristics of efficient EVCSs by comparing means of the inputs related to the groups classified by K-means clustering algorithm. This analysis presents that efficient EVCSs can be generally characterized with the high number of nearby EVCSs and low level of the traffic congestion.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.369-379
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• 2022

With the deepening integration of technology and cultural industries, China's digital cultural industry has begun to rise. The digital culture industry has met new demands for cultural consumption and brought new experiences to consumers in the digital economy era. This paper uses the public data of 36 Chinese A-share listed companies in digital culture from 2018 to 2019 to construct a technical innovation efficiency evaluation index system for listed companies in China's digital cultural industry. Through the use of data envelopment analysis (DEA) method, the technical innovation efficiency of 36 listed companies in China's digital cultural industry was evaluated. The research results show that: (1) China's 36 listed companies have low technological innovation efficiency; (2) the allocation of R&D resources of listed companies is unreasonable; (3) there is a large difference in technological innovation efficiency among listed companies. Therefore, it is necessary to increase the efficiency of technology innovation of listed companies in China's digital culture industry by investing more R&D funds, distributing R&D resources, establishing effective dynamic incentive mechanism, promoting government-industrial-academic research.