• Korean Journal of Organic Agriculture
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• v.17 no.1
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• pp.19-33
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• 2009

This paper evaluates the technical efficiency of organic farm management practices and studies its main determinants in Hongdongmyeon of Hongsung county, Chungnam province. The analysis is performed in two stages. First, the efficiency is measured via the nonparametric "Data Envelopment Analysis" (DEA) technique. The DEA models are constructed not only to assess the overall technical efficiency of organic fanning practices but also to evaluate the management efficiencies. In a second stage critical determinants of efficiency are determined using a Tobit model. In this analysis the focus is on technical and socio-economic variables. The analytical results show that technically efficient farms is about 13 percent and the mean technical efficiency is found to be 0.73 indicating that many farms are not operating at an efficient scale.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.367-378
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• 2021

This paper develops a dynamic regression model to quantify the contribution of key external factors to operational energy efficiency of ships. On this basis, kernel density estimation is applied to explore distribution patterns of fluctuations in operational performance. An empirical analysis based on these methods show that distribution of fluctuations in Energy Efficiency Operational Indicator (EEOI) is leptokurtic and fat tailed, rather than a normal one. Around 85% of fluctuations in EEOI can be jointly explained by capacity utilization and sailing speed, while the rest depend on other external factors largely beyond control. The variations in capacity utilization and sailing speed cannot be fully passed on to the energy efficiency performance of ships, due to complex interactions between various external factors. The application of the methods is demonstrated, showing a potential approach to develop a rating mechanism for use in the legally binding framework on operational energy efficiency of ships.

• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.507-514
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• 2015

The purpose of this study is to analyze the efficiency of resident companies in port hinterland logistics that are currently operating. The subjects of the efficiency analysis include 13 logistics hinterland resident companies in Incheon Port and Busan Port. Investment amounts, area, and number of employees were selected as input variables, and volume and sales amounts were selected as output variables. As for the efficiency analysis methods, traditional CCR and BCC models were applied. To overcome the limits of these models, a super-efficiency model and a Super-SBM model were also applied. According to the super-efficiency model analysis, the mean was 0.777 and the standard deviation was 0.54, indicating an approximate 33% difference of efficiency among the companies. According to the Super-SBM model analysis, the mean was 0.649 and the standard deviation was 0.489. When considering residuals in the super-efficiency model, the average efficiency score among the companies decreased by approximately 13%. This means that the efficiency score decrease of DMU, where non-radial residuals exist at about 18% on average. Examining the inefficiency of the inputs, the inefficiency of the number of employees turned out to be largest at -45%, compared to 'area' at -33% and 'investment amount' at -33%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.1022-1030
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• 1999

A numerical study was carried out to analyze the effect of flow distribution of stirred part and plug flow part on combustion efficiency at the coal gasification process in an entrained bed coal reactor. The model of computation was based on gas phase eulerian balance equations of mass and momentum. The solid phase was described by lagrangian equations of motion. The $k-{\varepsilon}$ model was used to calculate the turbulence flow and eddy dissipation model was used to describe the gas phase reaction rate. The radiation was solved using a Monte-Carlo method. One-step parallel two reaction model was employed for the devolatilization process of a high volatile bituminous Kideco coal. The computations agreed well with the experiments, but the flame front was closer to the burner than the measured one. The flow distribution of a stirred part and a plug flow part in a reactor was a function of the magnitude of recirculation zone resulted from the swirl. The combustion efficiency was enhanced with decreasing stirred part and the maximum value was found around S=1.2, having the minimum stirred part. The combustion efficiency resulted from not only the flow distribution but also the particle residence time through the hot reaction zone of the stirred part, in particular for the weak swirl without IRZ(internal recirculation zone) and the long lifted flame.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.2
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• pp.85-95
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• 2019

The internal environment in pig house is closely related to the animal productivity. In addition, it is important to consider a working environment inside the pig house due to high gas and dust concentrations. The poor working environment inside the pig house can cause health problems including respiratory diseases. To analyze the working environment, it is important to evaluate the ventilation efficiency to effectively remove harmful gases and dust. The purpose of this study is to develop a 3D CFD model to analyze the working environment in the pig house. CFD model was validated by comparing air temperature distributions between CFD computed and field measured data. The average air flow rate at the pig height was 40.1 % lower than the working height when incoming air was concentrated on upper layer by the installed ventilation system on the experimental pig house. Using the validated CFD model, the regional ventilation efficiency was computed by the TGD(tracer gas decay) method at the pig and working heights. There was a difference of ventilation efficiency on 14 % between the air stagnated section and the rest sections. Stagnated gas concentration can be effected by animal and human health.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.586-591
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• 2021

This paper proposes a mathematical model that can calculate the luminescence characteristics driven by alternating current (AC) power using the current-voltage-luminance (I-V-L) properties of organic light emitting devices (OLED) driven by direct current power. Fluorescent OLEDs are manufactured to verify the model, and I-V-L characteristics driven by DC and AC are measured. The current efficiency of DC driven OLED can be divided into three sections. Region 1 is a section where the recombination efficiency increases as the carrier reaches the emission layer in proportion to the increase of the DC voltage. Region 2 is a section in which the maximum luminous efficiency is stably maintained. Region 3 is a section where the luminous efficiency decreases due to excess carriers. Therefore, the fitting equation is derived by dividing the current density and luminance of the DC driven OLED into three regions, and the current density and luminance of the AC driven OLED are calculated from the fitting equation. As a result, the measured and calculated values of the AC driving I-V-L characteristics show deviations of 4.7% for current density, 2.9 % for luminance, and 1.9 % for luminous efficiency.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.3
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• pp.7-17
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• 2017

Loan consultants assist clients with loan application processing and loan decisions. Their duties may include contacting people to ask if they want a loan, meeting with loan applicants and explaining different loan options. We studied the efficiency of service quality of loan consultants contracted to a bank in Korea. They do not work as a team, but do work independently. Since he/she is not an employee of the bank, the consultant is paid solely in proportion to how much he/she sell loans. In this study, a consultant is considered as a decision making unit (DMU) in the DEA (Data Envelopment Analysis) model. We use a principal component analysis-data envelopment analysis (PCA-DEA) model integrated with Shannon's Entropy to evaluate quality efficiency of the consultants. We adopt a three-stage process to calculate the efficiency of service quality of the consultants. In the first stage, we use PCA to obtain 6 synthetic indicators, including 4 input indicators and 2 output indicators, from survey results in which questionnaire items are constructed on the basis of SERVQUAL model. In the second stage, 3 DEA models allowing negative values are used to calculate the relative efficiency of each DMU. In the third stage, the weight of each result is calculated on the basis of Shannon's Entropy theory, and then we generate a comprehensive efficiency score using it. An example illustrates the proposed process of evaluating the relative quality efficiency of the loan consultants and how to use the efficiency to improve the service quality of the consultants.

• Journal of Korea Trade
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• v.25 no.1
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• pp.169-183
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• 2021

Purpose - This paper analyzes the effect of the agricultural export market for Korea's new southern countries in consideration of logistics efficiency. In order to expand Korean agricultural exports, the logistics performance index, national income, per capita income, consumer price index, distance and FTA are included. Through empirical analysis, the impact of logistics efficiency on Korean agricultural exports is derived and measures are proposed to expand exports in the future. Design/methodology - The analytical model of this study takes into account the import demand factors of the new southern countries for Korean agricultural exports. A research model was established based on prior research based on the gravity model, which is widely used in international trade effect analysis. In particular, logistics efficiency measures the effect on Korean agricultural exports using the logistics performance index and examines the effect by deriving factors for export expansion. Findings - The main findings of this study can be summarized as follows: The higher the logistics efficiency of the new southern countries in exporting Korean agricultural products, the more directly they have an effect on expanding exports. In addition, it was analyzed that the expansion of Korean agricultural exports has a positive effect on the other countries' national income, per capita income, consumer price index, population, and FTA. Based on these results, the importance of efficient logistics management in agricultural exports has been emphasized. Originality/value - There are not many studies on the export of agricultural products by logistics efficiency. However, prior studies that have adapted to manufacturing and other areas suggest that logistics efficiency has a direct effect on exports. This study suggests that Korean agricultural products are directly effective in exporting to new southern countries in terms of logistics efficiency. This can be an important time point in recognizing that logistics capabilities are important to ensure new books and the safety of agricultural products.

• The Journal of the Korea Contents Association
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• v.21 no.11
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• pp.361-374
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• 2021

The purpose of this study is to analyze the efficiency and productivity of technological innovation activities of companies certified as innovative pharmaceutical companies by the government to diagnose their competitiveness and derive measures to strengthen them. This study collected pharmaceutical input (R&D expenditures and number of employees) and output (sale, operating profit and patent) data between 2017 and 2019 for 38 innovative pharmaceutical companies. This study analyzed them using the data envelopment analysis (DEA) method, Tobit model and the Malmquist Productivity Index (MPI). First, the DEA result of the innovative pharmaceutical companies show that between the value of the CCR model of the scale efficiency and the value of the BCC model to diagnose the internal operation efficiency is differences. Second, efficiency does not differ between corporate characteristics. Third, Tobit model shows that number of patents held have positive effects on efficiency. Forth, overall MPI is 0.89. This can be interpreted as the rate of TECI decreased 3%p and TCI has increased 4%p. The results of this study can be used as decision-making data for response strategies to improve efficiency by identifying the cause of inefficiency and presenting target values.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1109-1114
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• 2022

The SMART (System-integrated Modular Advanced ReacTor) is an integral-type small modular reactor developed by KAERI (Korea Atomic Energy Research Institute). This paper discusses the feasibility and applicability of a 3D-based equivalent model using dynamic condensation method for seismic analysis of a SMART control rod drive mechanism. The equivalent model is utilized for complicated seismic analysis during the design of the SMART. While the 1D-based beam-mass equivalent model is widely used in the nuclear industry for its calculation efficiency, the 3D-based equivalent model is suggested for the seismic analysis of SMART to enhance the analysis accuracy of the 1D-based equivalent model while maintaining its analysis efficiency. To verify the suggested model, acceleration response spectra from seismic analysis based on the 3D-based equivalent model are compared to those from the 1D-based beam-mass equivalent model and experiments. The accuracy and efficiency of the dynamic condensation method are investigated by comparison to analysis results based on the conventional modeling methodology used for seismic analysis.