• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.205-210
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• 2014

The micro grid considered in this paper consists of a diesel generator, a photovoltaic array, a wind turbine, a fuel cell, and a energy storage system. This paper explains and simulates the micro grid components in terms of accuracy and efficiency of having a system model based on the costs of fuel as well as operation and maintenance. For operational efficiency, the objective function in a diesel generator consists of the fuel cost function similar to the cost functions used for the conventional fossil-fuel generating plants. The wind turbine generator is modeled by the characteristics of variable output. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of micro grid. The operating cost in fuel-cell system includes the fuel costs and the efficiency for fuel to generate electric power. To develop the overall system model gives a possibility to minimize of the total cost of micro grid. The application of optimal operation can save the interruption costs as well as the operating costs, and improve reliability index in micro grid.

• Journal of Environmental Science International
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• v.13 no.4
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• pp.349-357
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• 2004

Emergy is a measure of the processes required to produce something expressed in units of the same energy form. Emergy based indices can provide insights into the thermodynamic efficiency of the process, the quality of its output, and the interaction between the process and its surrounding environment. However, in an industrial system, the inputs are mostly nonrenewable, renewable energy source is nearly zero, ultimate purpose is pursuit of profits in economic activity. In study, we present two indices based on emergy - EEE(Ecological Economic Efficiency) and ERI(Environmental Responsibility Index). The EEE is taken into account real value of product in market economy. The ERI is shown to be a function of the net yield of the economy, its ‘load’ on the environment and ecological economic efficiency. Manufacturing industry of Korea produced the 30% of total GDP in 2001. We applied these indices to manufacturing industry for environmental management and further sustainable industry. As a results, the highest ERI is 0.34 in recycling industries, the lowest ERI is 0.01 in coke, refined petroleum products which is dominated by ELR. The higher ERI, the more friendly to environment. The suggested indices help us understand relative contributions of various alternatives in company's production and consumption activity, and provide a tool of decision-making for the rearrangement of future industries. Furthermore, they contribute to environmental friendly operation and consumption.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.11
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• pp.1617-1621
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• 2002

Two hundred and sixteen single comb white egg layers of the White Leghorn hens of 24 weeks of age were randomly allocated to 12 groups with three replications of six hens in each. Hens were fed in a factorial arrangement 2${\times}3{\times}$2, on diets containing either 16 or 18% crude protein with 0, 3 or 6% fish meal, replacing groundnut meal with soybean meal. Soybean meal incorporation improved (p<0.05) egg production, feed intake, feed conversion efficiency and egg weights. Egg quality traits of specific gravity, shape index, albumen index, yolk index and shell thickness remained unchanged. Laying performance was significantly (p<0.05) better at 18% than on 16% dietary protein level. Use of fish meal linearly improved egg production and feed conversion efficiency on diets supplemented with groundnut meal and fish meal incorporation showed quadratic improvement on feed conversion efficiency with SBM diets at 16% dietary protein level. Therefore, use of soybean meal as substitute of groundnut meal is recommended in layer diets, at 16% dietary protein level and fish meal incorporation could be beneficial for layers.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.11
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• pp.1033-1039
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• 2020

Vietnam is conducting an export-led growth model and labour-intensive industries contributing majorly to the total export value. In the context of Industry 4.0, the labour-based industries are significantly affected; hence, enhancing productivity is the key measure to maintain these industries. The garment industry contributes significantly to the total export value of Vietnam. Based on meta-frontier framework, the approach of data envelopment analysis is used to measure technical efficiency of Vietnamese garment firms and the global Malmquist TFP index is utilised to identify productivity change and its components including efficiency, technology and technical gaps between different groups of firms. The data of Vietnamese garment firms from 2013 to 2018 collected from the Vietnam General Statistic Office is used in this study. The results show that: (i) The total factor productivity of Vietnamese garment firms growth, technical progress is the main contributor; (ii) The private garment sector is the leading group; (iii) There is a large technological gap among Vietnamese garment sectors. The private and FDI garment firms have experienced a growth in all components of total factor productivity change. Meanwhile, technological progress change is the main reason to constrain the productivity growth of state-owned garment firms.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.9
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• pp.487-493
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• 2004

The electric power industry throughout the world is undergoing considerable changes from the vertically integrated utility structure to the deregulated market. However, the deregulated electricity market is operated with respect to theory of economical efficiency, and therefore, the system operator requires data with fast contingency ranking for security of the bulk power system. This paper compares the weather dependant probabilistic risk index(PRI) with the system performance index for power flow in the IEEE-RTS. The system performance index for power flow presents the power system stability. This paper presents fast calculation method for determining contingency ranking using the weather dependant probabilistic risk index(PRI). The probabilistic risk index can be classified into the case of normal and adverse weather. This paper proposes calculation method using the probabilistic risk index in determining contingency ranking required for security under the deregulated electricity market.

• Industry Promotion Research
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• v.7 no.2
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• pp.59-73
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• 2022

This paper aims to analyze efficiency of sustainable development of foreign trade in eastern China to reduce the input while maintaining the current output level. This paper adopts relevant input-output indicators of 11 provinces in eastern China from 2016 to 2020 and uses DEA to measure comprehensive efficiency, pure technical efficiency, and scale efficiency from the input perspective. Malmquist index was used to calculate MPI. As a result, from 2016 to 2020, the MPI of all provinces in eastern China was 1.035, higher than 1, and the net technology efficiency was 0.911, lower than 1. Overall, the average technological progress index increased 4.5% to 1.045. It can be seen that the sustainable development efficiency of foreign trade has an overall influence on comprehensive efficiency, net technology efficiency, and scale efficiency. The efficiency of sustainable development of foreign trade in eastern China is mainly limited by its scale. The improvement of MPI in the eastern Region mainly benefits from technological progress. For provinces affected by internal factors, it is suggested to strengthen internal coordination. For provinces affected by external factors, it is suggested to respond appropriately to external factors.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.19-19
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• 2011

The appraisals of hydrology model behavior for flow and water quality are generally performed through comparison of simulated data with observed ones. To perform appraisal of hydrology model, some criteria are often used, such as coefficient of determination ($R^2$), Nash and Sutcliffe model efficiency coefficient (NSE), index of agreement (d), modified forms of NSE and d, and relative efficiency criteria NSE and d. These criteria are used not only for hydrology model estimations also for various comparisons of two data sets; This NSE has been often used for SWAT calibration. However, it has been known that the NSE value has some limitations in evaluating hydrology at watersheds under monsoon climate because this statistic is largely affected by higher values in the data set. To overcome these limitations, the SWAT auto-calibration module was enhanced with K-means clustering and direct runoff/baseflow modules. However the NSE is still being used in this module to evaluate model performance. Therefore, the SWAT Auto-calibration module was modified to incorporate alternative efficiency criteria into the SWAT K-means/direct runoff-baseflow auto-calibration module. It is expected that this enhanced SWAT auto-calibration module will provide better calibration capability of SWAT model for all flow regime.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.473-479
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• 2004

A sedimentation basin (SB) at the inlet of an irrigation reservoir which was constructed using an auxiliary dam was monitored to evaluate its pollutant removal efficiency. Water sampling at three points, i.e., inflow stream, upstream and downstream of the reservoir, were taken 5 times before and after the construction of the SB in 1999 and 2003, respectively. No significant water quality variations in inflow stream were observed during these periods. The COD, T-N, T-P and SS removal efficiencies were 38, 24, 35 and 49%, respectively. The results indicated that those removal efficiencies significantly increased during the rainy season and COD removal efficiency, especially, was higher than others studies. The scale of SB in this study was rational as aspects of pollutant removal efficiency and hydraulic detention time. And it is recommended that SB, at inlet of an reservoir, should be constructed as completely separated structure from reservoir water body and having SAR Index from 0.7% to 1.0%.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.542-547
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• 2009

The objective of this paper is to measure the relative technical efficiency of Korean railway transport service. Previous studies on the efficiency in Korean railway service have carried out before the structural reform of Korean railway industry in 2004, whereas this study used the latest data which reflected the impact of reform. We analyzed the efficiency in Korean railway transport by means of measuring the technical efficiencies of other countries, these were estimated with data envelopment analysis. Using data from 22 railway operators over the period $2000{\sim}2006$, the results indicate that the Korean railway transport has been operated efficiently as compared with others.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.47-51
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• 2014

In this paper, unit cell and arrayed cover for improving the transfer efficiency of resonant wireless power transfer system is proposed. We used the characteristic of zero refractive index for focusing a magnetic field between the transmitting resonator and receiving resonator. For zero refractive index, we designed the unit cell structure that have a negative value of effective permeability. The size of proposed unit cell based on metamaterial structure is $70mm{\times}70mm{\times}3.2mm$, operating frequency is 13.56 MHz. And, the size of arrayed cover is $400mm{\times}400mm{\times}3.2mm$, is consists of 2-layers. The transfer efficiency of the proposed wireless power transfer system are 94.8 %, 93.2 %, 91.4 %, 90.8 % at 100 mm, 200 mm, 300 mm and 400 mm (distance between transmitting and receiving resonator), respectively. And proposed WPT system has a transfer efficiency high than 90 % over the overall distances.