• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.676-681
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• 2015

Recently many studies being carried out to increase the light efficiency of LED. The external quantum efficiency of LED, generally the light efficiency, is determined by the internal quantum efficiency and the light extraction efficiency. The internal quantum efficiency of LED was already reached to more than 90%, but the light extraction efficiency is still insufficient compared with the internal quantum efficiency because the total internal reflection is generated in the interface between the LED chip and air. Thus, we studied about flip chip LED with PSS and performed the optical simulation which find more optimized PSS for flip chip LED to increase the light extraction efficiency. Decreasing of the total internal reflection and effect of diffused reflection according to PSS improved the light extraction efficiency. To get more higher the efficiency, we simulated flip chip with PSS that the parameters are arrangement, edge spacing, radius, height and shape of PSS.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.895-904
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• 2021

This study aims to investigate the impact of innovation on firm efficiency. Panel data of fourteen finance companies and nine technology companies from 2011 to 2019 on the Vietnam Stock Exchange Market is derived from audited financial statements, annual reports, and other crucial reports that are provided by Vietstock; macroeconomic variables are collected from the World Bank Database. A two-stage approach is used. First, use of the Data Envelopment Analysis methodology to measure firm efficiency. Second, use of the Pooled ordinary least squares, the Fixed effects model, and the Random effects model to investigate the impact of innovation on firm efficiency. Furthermore, the Generalized Method of Moments and the Tobit model are used to validate the impact of innovation on firm efficiency, and the t-test is used to confirm the difference in efficiency with and without the impact of innovation between two industries. The results show that there is a significant impact of innovation on efficiency, and innovation plays a more important in increasing the efficiency of the finance industry than the technology industry. Moreover, the relation between age and efficiency is like the U-shaped, and between size and efficiency is like the inverted U-shaped, whereas efficiency is not associated with inflation.

• The Research Journal of the Costume Culture
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• v.17 no.5
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• pp.746-757
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• 2009

This study is focused on the elucidation of efficient and correct marking methods by comparing and analyzing marker efficiency depending on the marking job condition such as interval of checking-pattern, width of materials, and marker orientation using man's shirts. To compare the marking efficiency of shirts, plain and check-patterned materials with the intervals of $1.5{\times}1.5cm$, $3{\times}3cm$, and $5{\times}5cm$ were selected. First, in the comparison of marking efficiency depending on materials width, the highest efficiency was obtained with nap-either-way position of 150cm, plain materials and lowest efficiency with nap-one-way position of 150cm, $5{\times}5cm$ check-pattern materials. Regardless of the direction of marker position, the marking efficiency of 150cm width was higher than 110cm width in the plain, $1.5{\times}1.5cm$ and $3{\times}3cm$ check-pattern interval, but the marking efficiency of 110cm width was higher than 150cm width in the $1.5{\times}1.5cm$ check-pattern interval. Second, in the comparison of marking efficiency depending on the direction of marker position, regardless of check-pattern interval and material width, the highest efficiency was obtained with nap-either-way position. And nap-up-and-down and nap-one-way follows next. Third, in the comparison of marking efficiency depending on check-pattern interval, the efficiency of plain materials was higher than those of check-patterned materials. And increasing the intervals decreased marking efficiency and vice versa. So the lowest efficiency was obtained with $5{\times}5cm$ check patterned materials.

• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.659-669
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• 2008

Two sets of four parallel activated sludge reactors (ASRs) maintaining an MLSS of 3000 mg/L were operated to investigate the effect of DO, HRTs and bio-contact media (BCM) packing ratios on the removal efficiency of organic matters and nitrogen. Packing ratios of BCM to BCM-ASR systems 1, 2, 3, and 4 were 0% (suspended growth only), 10%, 15% and 20%, respectively. All systems were operated at an HRT of 4 hr, 6 hr, and 8 hr, respectively; DO concentration was maintained 0.5~1.0 mg/L and 1.5~2.0 mg/L for each HRT condition. In terms of TSS, TCODcr and SCODcr removal efficiency, all systems had a similar level of the removal efficiency under varied HRTs, and DO. But organic removal efficiency of systems with BCM was approximately 3~5% higher than systems without BCM at the same HRT and the DO. About the nitrification efficiency, with high DO (1.5~2.0 mg/L), as HRT (4 hr, 6 hr, 8 hr) or BCM packing ratio increased, the slight increment of nitrification efficiency was observed. However, under the low DO (0.5~1.0 mg/L), increase of BCM packing ratio and HRT resulted in large increase of the nitrification efficiency. At the same HRT and BCM packing ratio, the nitrification efficiency increased greatly with up to 15% as DO increased. When the HRT increased from 4hr to 8hr, the denitrification efficiency slightly increased by 5~10% only, under all DO conditions. Systems with BCM had higher denitrification efficiency, ranged 62.7~91.1% than systems without BCM showed 32.1~65.6%. And the increase in BCM packing ratio from 10% to 20% resulted in about 14~16% denitrification efficiency increment. BCM packing ratio showed great effect on the denitrification. The increase of the DO (from 0.5~1.0 mg/L to 1.5~2.0 mg/L) at the same HRT and BCM packing ratio resulted in slight decrease of denitrification efficiency with up to 7% for systems with BCM. But for systems without BCM, the denitrification efficiency decreased with up to 28%. In all system, the denitrification efficiency had more influence on the TN removal efficiency than nitrification efficiency. So, BCM packing ratio (0%, 10%, 15%, 20%) has greater effect on the TN removal than HRT and DO. The TN removal efficiency increased as packing ratio of BCM increased with up to 45%. As a result, the highest TN removal efficiency was observed 73.7% at the condition showed the highest denitrification efficiency that DO of 0.5~1.0 mg/L, an HRT of 8 hr, and 20% of BCM packing ratio was maintained.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.65.1-65.1
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• 2010

Thermal performance tests of solar thermal collectors include determination of coefficient parameters in an efficiency equation. The parameters can be estimated using regression method to minimize an objective function as sum of differences between measured efficiency data and regressed efficiency equation. However, this conventional approach doesn't consider measurement uncertainties. In this presentation, a method to determine regression parameters in the efficiency equation and uncertainties of the parameters is described with mainly mathematical expressions based on literature reviews. In the method, parameters in the equation for collector efficiency can be determined using regression analysis with a weighting factor in the objective function. The weighting factor can be uncertainties of the differences between measured and fitted efficiencies. To evaluate the approach, performance estimation of a solar collector using the efficiency equation with uncertainties is compared to the result using the conventional efficiency equation by a simulated way for a case in one of previous studies.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.213-217
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• 2001

This paper deals with the estimation of efficiency of Telecommunication Operators(TOs) using DEA (Data Envelopment Analysis). The measure of efficiency using DEA accomplishes next two steps. First, the efficient frontier is derived using the data of input and output. And then the efficiency of the decision making units are measured by the distances from this frontier To measure efficiency, we consider a one-output, three-input production function. We use the tangible assets, investment cost, the number of employees for input data and measure the output by the revenue. After measuring the efficiency, We can compare the domestic TOs with the international TOs and the wire TOs with wireless ones by average efficiency. After accomplishing the analysis of efficiency, the internal/external efficiency is measured simultaneously through correlation between efficiency and profitability, quality level.

• Korean Journal of Organic Agriculture
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• v.25 no.4
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• pp.679-697
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• 2017

This study analyzes an economic efficiency of environmental friendly farm and conventional farm using the data envelopment analysis (DEA). We compare the economic efficiency of Environmental Friendly farm and Conventional farm. We also analyze the effects of some explanatory variables on allocative efficiency (AE), pure technology efficiency (PTE) and scale efficiency (SE). In the case of strawberries farm, environmental friendly farm has higher overall efficiency (OE) than conventional farm. But tomatoes farm has higher overall efficiency (OE) than conventional farm. And We measure returns to scale of farms. Most strawberries and tomatoes farms showed Increasing to Scale (IRS).

• Journal of the Korea Safety Management & Science
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• v.16 no.4
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• pp.359-369
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• 2014

Due to the severe market conditions, pre-entrepreneur seeks to start their business through franchise company. This paper, using the data envelopment analysis(DEA) method, examines efficiency of a group of franchise company in order to provide efficiency information with pre-entrepreneur. Output-oriented DEA model is applied in the investigation of efficiency, and the overall efficiency score is decomposed into pure technical efficiency and scale efficiency. The input variables selected to evaluate the efficiency are franchise deposit, franchise contribution cost and the output variables are sales and number of franchises, and length of business. The results of this paper show franchise industry have the low level of overall efficiency and the main sources of inefficiency is found technical rather than scale. As a result, this paper provides not only the current status of efficiency information of a franchise with pre-entrepreneur but also give warning when they sign-up with franchise business.

• Korea Journal of Hospital Management
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• v.4 no.2
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• pp.219-241
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• 1999

This study used the Data Envelopment Analysis, a mathematical linear programming method, to evaluate cost efficiency of hospitals in Korea. DEA method was applied to 244 hospitals: 31 bankrupt hospitals and 213 survived hospitals. Among the 213 sound hospitals, 11 hospitals showed efficiency score 100, but more than 40 hospitals recorded efficiency scores lower than 60. This result implies that more hospitals can be bankrupt in the restructuring process of the industry within 1-2 years. Among the 31 bankrupt hospitals, the highest technical efficiency score was 0.821 and 11 hospitals showed technical efficiency lower than 0.6. This implies that selective financial support based on cost efficiency by the government will be valuable to prevent bankruptcy of these hospitals. The logistic analysis showed statistically significant relationship between bankruptcy and efficiency of hospitals in Korea.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.4
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• pp.1-7
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• 2006

A water hydraulic pump is likely to have serious problems of high leakage, friction and low energy efficiency. A water hydraulic pump has commonly a fixed displacement type and its outlet flow is adjusted by controlling rotation speed of the pump, which can be implemented by using an electric inverter. This study aims to investigate energy efficiency of the water hydraulic pump system which is driven by an electric inverter. The study is based on the experimental results. The pump which is used in the study shows relatively good efficiency and low leakage, low friction as well. The reasons for the good performance of pump is also investigated.