• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1591-1593
• /
• 2008

The tubular field emission lamp (FEL) was developed using a wire type carbon-nano-structure emitter called CNX The luminous efficiency of the tubular FEL (diode type, diameter: ${\varphi}15.5mm$, length: 200mm) has already achieved around 45lm/W and we expect to achieve over 60lm/W within the year.

• Advances in Energy Research
• /
• v.4 no.4
• /
• pp.275-284
• /
• 2016

In the present work, ZnO nanoparticles (NPs) have been dispersed alone in the same solvent of the active layer for improving performance parameters of the organic solar cells. Different concentrations of the ZnO NPs have been blended inside active layer of the solar cell based on poly(3-hexylthiophene) (P3HT), which forms the hole-transport network, and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which forms the electron-transport network. In the present investigations, the ZnO NPs may represent an efficient tool for improving light harvesting through light scattering inside active layer, electron mobility, and electron acceptance strength which tend to improve photocurrent and performance parameters of the investigated solar cell. The fill factor (FF) of the ZnO-doped solar cell increases nearly 14% compared to the non-doped solar cell when the doping is 50%. The present investigations show that ZnO NPs improve power conversion efficiency of the solar cell from 1.23% to 1.64% with increment around 25% that takes place after incorporation of 40% as a volume ratio of the ZnO NPs inside P3HT:PCBM active layer.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.4
• /
• pp.239-247
• /
• 2021

Conventional banks are often considered more efficient than Islamic banks because they have been operating for decades, but Islamic banks have shown rapid development recently. Therefore, this study mainly aims to compare the level of efficiency of conventional banks and Islamic banks and which ones have the best level of efficiency. This study employs panel data using Stochastic Frontier Analysis (SFA) as the data analysis technique. The data used is annual data from 13 conventional banks and 13 Islamic banks in Indonesia during the 2014-2019 period. The result shows no significant difference in the efficiency of conventional banks and Islamic banks. This result is presumably influenced by the small size of the bank and the total number of banks used in the study. The data used in the study is limited to the period from 2014 to 2019. The variables utilized are also limited to the availability of financial report data which is publicly published. This study provides additional empirical evidence regarding conventional banks' and Islamic banks' efficiency in Indonesian banking by using the latest data. While theoretically, Islamic banks are expected to be more efficient than conventional banks, this study did not find any strong support for the case in Indonesia during the observation period.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.35 no.2
• /
• pp.19-35
• /
• 2010

Many papers have used a two-stage approach of first calculating DEA efficiency scores and then seeking to correlate these scores with various environmental variables. Most of the studies have not checked whether such a two-stage approach is statistically valid for identifying significant environmental variables. Recently Simar and Wilson (2007) (SW) introduce a sensible data generating process and bootstrap procedure based on truncated regression for the two-stage approach. Banker and Natarajan (2008) (BN) provide a statistical foundation for the two-stage approach comprising a DEA followed by an ordinary least squares or maximum likelihood estimation. Researchers have to identify an approach suitable for their research circumstances in terms of properties, merits, demerits, and robustness to plausible departures from its chosen data generating process. We summarize the foundations and properties of the two-stage procedures suggested by SW and BN. And we discuss merits and demerits of those procedures. Also using Monte Carlo simulation we assess their relative performance under several misspecified settings.

• Journal of Korea Technology Innovation Society
• /
• v.4 no.3
• /
• pp.369-382
• /
• 2001

In this research, the world top steel companies' technical changes were measured by the nonparametric Malmquist index. Steel industry's production frontier which was composed of multiple inputs and multiple outputs was defined by using real data of the companies from 1986 to 1998, and then the variability of technical progress(or regress) was analyzed during that period. The dynamics of individual steel companies\` technical changes, periodical technical changes, and each country's technical chanties were explained. A matrix which was based on technical chanties, technical efficiency changes, and scale efficiency changes was designed to assist to find out current position and In build up future strategies. This research results will be an valuable input to the early stage of formulating competitive strategy because the technical core capability is an important source of the each companies's competitiveness.

• IE interfaces
• /
• v.19 no.4
• /
• pp.291-299
• /
• 2006

In order to enhance sustainable war fighting capabilities, it is important to maintain a good ammunition support system. In this paper, we evaluate the performance of ammunition companies using Imprecise Data Envelopment Analysis (IDEA)-BCC and IDEA-Additive model, which can deal with imprecise data in DEA. The input variables of IDEA models were selected by stepwise multiple regression analysis. With the regression model, we could choose the number of soldiers, officers, and ammunition warehouses as input variables that have significant effects on the output performance. Then, we applied the IDEA-BCC model with the concept of potential efficiency. The results of the model indicate that 8 out of 16 ammunition companies are efficient, 7 are inefficient, and 1 is potentially efficient. We could also identify the possible input excesses and output shortfalls to reach the efficient frontier using the IDEA-Additive model.

• Journal of the Korea Safety Management & Science
• /
• v.5 no.4
• /
• pp.267-278
• /
• 2003

Data Envelopment Analysis-Assurance Region(DEA-AR) model is used in this paper to investigate the efficiency and performance potential of Korean banks as they engage in activities that incur interest and non-interest expenses and produce income. DEA provides a measure of each bank's relation to the best-practice frontier for its competitors. This can provide a better quality-benchmark than using industry averages or a particular peer bank branches as the benchmark. The banks are classified into efficient and inefficient sets. Multiplier values for AR-inefficient banks with unique slacks indicate the potential for management to improve the bank's performance relative to its peers. DEA-AR that provide economically reasonable bounds for the multipliers lead to profitability potential, as distinct from efficiency, results.

• Computers and Concrete
• /
• v.30 no.1
• /
• pp.33-42
• /
• 2022

Experimentally predicting the compressive strength (CS) of concrete (for a mix design) is a time-consuming and laborious process. The present study aims to propose surrogate models based on Support Vector Machine (SVM) and Gaussian Process Regression (GPR) machine learning techniques, which can predict the CS of concrete containing nano-silica. Content of cement, aggregates, nano-silica and its fineness, water-binder ratio, and the days at which strength has to be predicted are the input variables. The efficiency of the models is compared in terms of Correlation Coefficient (CC), Root Mean Square Error (RMSE), Variance Account For (VAF), Nash-Sutcliffe Efficiency (NSE), and RMSE to observation's standard deviation ratio (RSR). It has been observed that the SVM outperforms GPR in predicting the CS of the concrete containing nano-silica.

• Environmental and Resource Economics Review
• /
• v.30 no.4
• /
• pp.581-605
• /
• 2021

The purpose of this study is to provide basic data for improving energy efficiency by estimating the regional energy efficiency in Korea using the stochastic frontier approach beyond the energy intensity that has been traditionally used as an indicator of energy efficiency. In this paper, energy efficiency and energy intensity efficiency were estimated as a stochastic distance function from 1998 to 2018 for 16 cities and provinces in Korea. In addition, the robustness of energy efficiency according to the capital stock estimation methods which had been mixed in previous studies was reviewed. As a result of the analysis, there is a significant change in regional rankings according to the three energy efficiency indicators, so they should be used complementary to each other. Second, while the energy efficiency improved little by little over time, the energy intensity efficiency decreased slightly though. Lastly, energy efficiency by region according to the capital stock estimation method was not robust. Care must be taken in estimating capital stock, which is important in economic analysis.

• Journal of Korean Society for Quality Management
• /
• v.37 no.4
• /
• pp.61-70
• /
• 2009

This paper introduces quantitative tools for evaluating the relative efficiency of Career & Counseling Jobs in universities. As tools, it uses Data Envelopment Analysis (DEA) developed by Charnes and Cooper. It finally selects 29 DMUs which are listed on the Ministry Of Education, Science And Technology(http://academyinfo.go.kr). We measures the technical efficiency of each DMU with the use of DEA-CRS, rather then DEA-VRS because DEA-CRS not only compares relative efficiencies but also implicitly considers economies of scale based on the assumption of linearity. We run a linear programming model Frontier Analyst Program for the estimation of the relative efficiencies of each DMU. The model also indicates the precise amount of inefficiencies for each input, which mean how much inputs are wasted for a given output and how much the university is inefficiently operated. This analysis helps to give guideline for the organization to construct a futureoriented operational strategy and also to show clear picture of contents of mismanagement for the past. The details of mismanagement are to be identified, analysed and finally corrected.