• Journal of Korean Society of Transportation
• /
• v.22 no.4 s.75
• /
• pp.7-18
• /
• 2004

There have been various research in analyzing airport productivity such as measuring total factor productivity using the models of translog cost function. DEA(Data Envelopment Analysis) model is very useful in measuring productivity with linear programming when the output is not clearly identified and measured quantitatively in such complex facilities as airport. This study is to measure airport productivity using DEA approach for Northeast Asia. Seven international airports were analyzed including Incheon International Airport in Korea, Cheklapkok Airport in Hongkong, Narita Airport in Japan, and Changi Airport in Singapore. With the productivity measured, we can identify one of the important aspects of comparative advantage in hub competition in Asia.

• The Journal of the Korea Contents Association
• /
• v.13 no.12
• /
• pp.357-368
• /
• 2013

This research explores the efficiency of social welfare expenditure in Korea by analyzing marginal productivity, scale economies, and elasticity of substitution that could be obtainable from a production function. By virtue of VES production function, such productive indicators are easily identified. If once the efficiency is revealed in the production process, it brings to a positive impact to increase the level of income. Empirical evidences are shown that the public expenditure is operated systematically in comparing with the private one. This is mainly due to the fact that the system of the public sector is well-established. It implies that an operational system for the private sector ought to be built up in a short period of time. Otherwise, increasing in expenditure by a private sector would not be helpful to improve efficiency in the production side. Accordingly, level of income.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.9
• /
• pp.818-826
• /
• 2012

In this paper, the improvement methods of the computational efficiency of the conjunction screening algorithm, which calculates the closest distance between primary satellite and space objects are presented. First method is to use GPU(Graphics Processing Unit) that has high computing power and handles quickly large amounts of data. Second method is to use Apogee/Perigee filter which excludes non-threatening objects that have low probability of collision and/or minimum distance rather than that of thresh hold. Third method is to combine first method with second method. As a result, the computational efficiency has been improved 34 times and 3 times for the first method only and second method only, respectively. On the contrary, the computational efficiency has been dramatically improved 163 times when two kinds of methods are combined.

• Resources Recycling
• /
• v.24 no.2
• /
• pp.69-78
• /
• 2015

Recently, the importance of efficient resource management has been highlighted due to the uncertainty of its security. Developed countries promote the legislative provision and transition of industrial structure to maximize the efficiency of resource use through supporting the sustainable resource management at national level. Meanwhile Korea has very sensitive industrial structure along with the international resource supply and demand conditions. It is acutely necessary to improve the resource productivity with the various action plans such as the increase of recycling rate and the establishment of methodical resource management system. Especially, the study on the direction of each flow stage and the concrete action plans for using resource efficiently in the life-cycle of resource will be required. Therefore, this study suggests the future direction of each flow stage(production stage and circulatory stage), and the concrete action plans to improve the present problems of resource management in Korea.

• Journal of Navigation and Port Research
• /
• v.31 no.1 s.117
• /
• pp.89-97
• /
• 2007

This paper presented a approach to the measurement of efficiency in container terminals in Korea. To perform this objective, it used Data envelopment analysis(DEA) which has particular applicability in the service sector. DEA as mathematical programming techniques enables relative efficiency ratings to be derived within a set of analysed units. So this paper investigated the efficiency employing DEA-CCR and DEA-BCC Model on data for 15 container terminals from 1998 through 2005. Results of this paper, suggested to some plan for operation strategy in Container terminals.

• Review of Culture and Economy
• /
• v.19 no.2
• /
• pp.171-193
• /
• 2016

China's advertising industry has rapidly increased owing to economic growth and big market size. This paper covers the localization and relative efficiency in the Chinese advertising industry. To analyze localization level and efficiency of advertising industry, this paper uses Location Quotient(LQ) and Data Envelopment Analysis (DEA) respectively. According to the results, the first finding shows that the higher regional development level have the relative efficiencies, the higher regional development level also have regional specialization degree. The second finding indicates that Chinese advertising industries are multipolalized region by region. The last finding reveals that advertising industry of middle and west regions has long term development potentiality owing to high specialization degree with low relative efficiencies.

• The Journal of the Korea Contents Association
• /
• v.19 no.7
• /
• pp.99-109
• /
• 2019

Data Envelopment Analysis (DEA), a non-parametric productivity analysis tool, has become an accepted approach for assessing efficiency in a wide range of fields. Despite of its extensive applications, some features of DEA remain bothersome. For example DEA is good at estimating "relative" efficiency of a DMU(Decision Making Unit), it only tells us how well we are doing compared with our peers but not compared with a "theoretical maximum." Thus, in order to measure efficiency of a new DMU, we have to develop entirely new DEA with the data of previously used DMUs. Also we cannot predict the efficiency level of the new DMU without another DEA analysis. We aim to show that DEA can be used to evaluate the efficiency of ports and suggest the methodology which overcomes the limitation of DEA through hybrid analysis utilizing DEA along with C5.0. We can generate classification rules C5.0 in order to classify any new Port without perturbing previously existing evaluation structures by proposed methodology.

• Applied Chemistry for Engineering
• /
• v.33 no.1
• /
• pp.78-82
• /
• 2022

Inorganic-organic hybrid perovskite solar cells have demonstrated considerable improvements, reaching 25.5% of certified power conversion efficiency (PCE) in 2020 from 3.8% in 2009 comparable to silicon photovoltacis. However, there remains important concern on the stability of perovskite solar cells under environmental conditions that should be solved prior to commercialization. In order to overcome the problem, we have introduced a small amount of octylammonium iodide with longer alkyl chain than volatile methylammonium iodide into MAPbI₃ perovskites. The presence of octylammonium into perovskites were confirmed using Fourier-transform infrared spectroscopy and UV-visible spectroscopy. Moreover, octylammonium-modified perovskite solar cells showed a PCE of 16.6% and enhanced moisture stability with an increased contact angle of 72.2° from 57.0°. This work demonstrated the importance of perovskite compositional engineering for improving efficiency and stability.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.421-421
• /
• 2021

도시화, 산업화로 인해 하수처리장 유입하수 내 질소 농도가 증가하면서 그에 따른 부영양화 발생, 수생태계에 독성을 미치는 등의 악영향 또한 증가하게 되었다. 하수 내 고농도 질소를 처리하기 위해 1990년 초 연구가 시작되어 현재 보편적으로 사용되고 있는 생물학적 질소 제거 공정은 산소공급과 외부탄소원 보충 과정에서 상당한 비용이 소요된다. 이와 같은 문제점이 대두됨에 따라 고도의 질소 제거 공정이 요구되면서, 경제적으로 개선이 이루어져 기존의 질산화·탈질 공정보다 효율적인 혐기성 암모늄 산화 공정(ANaerobic AMMonium OXidation, ANAMMOX)이 제안되었다. ANAMMOX 공정은 혐기성 조건 아래 전자공여체와 전자수용체로써 암모니아성 질소와 아질산성 질소를 이용해 질소가스 형태로 질소를 제거하는 공정이다. 질산화·탈질 공정과 비교했을 때, 폭기과정에서의 산소요구량 감소, 외부탄소원 불필요, 질소 제거 과정 단축 등의 장점을 가진다. 본 연구는 수처리공정에서의 ANAMMOX 공정의 적용 가능성을 확인하고, 암모니아성 질소대비 아질산성 질소 비율에 따른 Mainstream ANAMMOX 공정의 효율 비교를 통해 공정의 안정성과 높은 제거효율을 확보할 수 있는 NH₄⁺ 대비 NO₂^- 비율을 도출하는데 목적이 있다. 실험실 규모의 Mainstream ANAMMOX 반응조에 적용한 비율은 선행연구를 비롯한 화학양론식에서 제시된 비율을 바탕으로 산정하였다. 1.00부터 1.30의 전체적인 비율을 Initial과 Advanced 2개의 구간으로 나누어 운전한 결과, 각 구간의 NH₄⁺ 제거효율은 각각 58~86%, 94~99%였다. NH₄⁺ 대비 NO₂^- 비율이 증가함에 따라 공정의 안정성이 확보되고, NH₄⁺ 및 총질소(TN) 제거효율이 증가하는 경향이 나타났다. 본 연구의 결과는 수처리공정에서의 안정적인 ANAMMOX 공정 적용을 유도하고, ANAMMOX 공정의 성능개선을 도모하는 연구의 기초로 활용될 수 있다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.6
• /
• pp.2455-2464
• /
• 2013

This study is focused on the effect of reformation of public transportation system on the efficiency of bus route system as a result of change of government subsidy scheme. Two types of government subsidy scheme has been considered and before and after analysis by Data Envelopment Analysis technique has been carried out for bus routes in Ulsan Metropolitan City. The analysis output has shown that there is no clear evidence to clarify the relationship between the change of government subsidy scheme and the efficiency of bus route system. There are two types of backgrounds may be suggested for this situation such as more longer period necessary to identify the policy effect and limitation to increase the number of passenger in a provincial city. Tobit regression analysis has also been conducted to discover the most effective variables for maximum efficiency and three variables including route length, frequency per vehicle per day, and headway are found to be influential. It is also seen that strategy to minimising input factors and service upgrade plan such as shortened route length and headway, increasing frequency per vehicle are necessary to develop the efficiency of bus routes operated in Ulsan city.