• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.49-55
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• 2012

In order to derive the efficient utilization of low pressure compressed air fogging system, cooling efficiencies with control types were analyzed through cooling experiments in tomato greenhouses. The control types were set up with temperature control, humidity control, temperature and humidity control, and time control. It showed that the cooling effects were 0.7 to $3.3^{\circ}C$ on average and maximum of 4.3 to $7.0^{\circ}C$, the humidification effects were 3.5 to 13.5 % on average and maximum of 14.3 to 24.4 %. Both the cooling and humidification effect were the highest in the time control method. The cooling efficiency of the air fogging system was not high with 8.3 to 27.3 % on average. However, the cooling efficiency of 24.6 to 27.3 % which appears from the time control is similar to the cooling efficiency of high pressure fogging system experimented in Japan. The air fogging system is operated by low pressure, but its efficiency is similar to high pressure. We think because it uses compressed air. From this point of view, we suggest that the air fogging system can get the cooling efficiency of similar levels to that of high pressure fogging system and it will have an advantage from clogging problem of nozzle etc.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.309-314
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• 2009

The unpredicted worldwide oil price makes the energy efficiency technology be more importance than any other period. The small cogeneration system is one of the most representative technology among the energy efficiency technologies, and the Stirling engine cogeneration system has been concerned and investigated due to the preferable characteristics - low toxic emission, low noise and vibration level, and the various form of fuel. A tiny, 1kW of electrical output, gas fueled Stirling engine cogeneration system was investigated. The electrical efficiency and thermal efficiency of the system were measured. The experiment was executed at an independent Stirling engine mode, independent secondary burner mode, and the combined mode. Part load characteristics of the Stirling engine cogeneration system were investigated also. With the efficiency characteristics, the $O_2$ and NOx emission characteristics were measured.

• Journal of Korean Society for Quality Management
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• v.26 no.3
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• pp.100-107
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• 1998

To evaluate the total quality activities is the most fundamental and critical process as one of the PDCA cycle. The quality award criteria such as Malcolm Baldrige National Quality Award and Deming Award can be a, pp.ied to the guideline for evaluating quality activities. We can identify several important factors for TQM by referring quality award criteria, but they don't suggest how efficiently implement TQM. In this paper, two methodologies are a, pp.ied to evaluate the TQM activities comparatively. One of them is the traditional scoring system (TSS) by analytic hierarchy process (AHP). TSS is the system which evaluates the performance of TQM by the weighted sum of critical success factors. Several quality award system are typical examples of TSS. The other is the efficiency measuring system (EMS) by data envelop analysis (DEA). DEA outperformed other alternative methods to measure the efficiency and it can be a, pp.ied to evaluate the TQM activities. The evaluation system by DEA can be named as EMS. The objective of this paper is to suggest a model called TAE (Total quality management Activities Evaluation), for evaluating TQM activities. In this model TQM organizations are classified into four types by considering TSS and EMS. Those types are high weighted sum and high efficiency type, high weighted sum and low efficiency type, low weighted sum and high efficiency type, and low weighted sum and low efficiency type. Therefore TQM organizations must not only make efforts to get the higher scores in terms of TSS, but also take necessary steps to enhance their efficiencies.

• Journal of Power Electronics
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• v.16 no.2
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• pp.666-674
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• 2016

In this paper, a high efficiency satellite electrical power supply system is proposed. The increased efficiency of the power supply system allows for downscaling of the solar array and battery weight, which are among the most important satellite design considerations. The satellite power supply system comprises two units, namely a generation unit and a storage unit. To increase the efficiency of the solar array, a maximum power point tracker (MPPT) is used in the power generation unit. In order to improve the MPPT performance, a novel algorithm is proposed on the basis of the hill climbing method. This method can track the main peak of the array power curve in satellites with long duration missions under unpredicted circumstances such as a part of the array being damaged or the presence of a shadow. A lithium-ion battery is utilized in the storage unit. An algorithm for calculating the optimal rate of battery charging is proposed where the battery is charged with the maximum possible efficiency considering the situation of the satellite. The proposed system is designed and manufactured. In addition, it is compared to the conventional power supply systems in similar satellites. Results show a 12% increase in the overall efficiency of the power supply system when compared to the conventional method.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.2
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• pp.73-84
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• 2018

This study sought efficiency of collaboration between manufacturers and distributors by finding a way to improve logistics efficiency in order to save distribution cost and standardize packaging together with profit generation by way of simple-display packaging in discount stores. For the study purpose, the impact of products with RRP (Retail Ready Packaging) by each discount store on the collaboration achievement such as loading efficiency was observed. From this observation, an alternative packaging system that can improve logistics efficiency between manufacturers and distributors was sought and the role of distributors in distribution standardization was explored. The purpose of this study also includes suggesting some implications on future basic direction of environment-friendly management. If this study would induce distributors to have more interest in distribution standardization and if logistics efficiency would be enhanced by the operation of packaging system considered of compatibility with pallets, this study would have academic significance and create practical values.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.119-130
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• 2013

A system with $n$ components which functions when at least ${\kappa}$ of the components function is called ${\kappa}$-out-of-$n$ system. Most studies on ${\kappa}$-out-of-$n$ system derive the system reliability based on the assumption that the system has just two states: functioning or failed. However, the system efficiency may depend on the number of functioning components. This paper considers a Multi-state ${\kappa}$-out-of-$n$ system and derives the total system efficiency. In addition, assuming that the system is repairable, the optimal repair policy to maximize the system efficiency is studied. The system efficiency considered in this paper can be regarded as a generalized measure of the mean time to the failure of the system.

• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.1-10
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• 2012

A photovoltaic/thermal (PVT)solar system is the solar technology that allows for simultaneous conversion of solar energy into both electricity and heat. This paper compared the performance of PVT system with a conventional PV module and solar collector and analyzed electrical and thermal efficiency of PVT system in terms of solar irradiance and inlet temperature of the working fluid. Based on the experimental data, thermal and electrical efficiencies of he glazed PVT system were57.9% and14.27% under zero reduced temperature condition which were lower by 13.6% than the solar thermal absorber plate and by 0.08% than the PV module respectively. For the unglazed PVT system it had lower thermal efficiency than the solar thermal absorber plate but higher electrical performance than the PV module due to the cooling effect by the working fluid. However, total efficiency of the glazed PVT system was72.2% which was higher than combined efficiencies of the solar collector and PV module. Besides, total efficiency of the PVT system would be much higher if calculated based on unit area.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.60-67
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• 2011

A photovoltaic/thermal(PVT)solar system is the solar technology that allows for simultaneous conversion of solar energy into both electricity and heat. This paper compared the performance of PVT system with a conventional PV module and solar collector and analyzed electrical and thermal efficiency of PVT system in terms of solar irradiance and inlet temperature of the working fluid. Based on the experimental data, thermal and electrical efficiencies of the glazed PVT system were 57.9% and 14.27% under zero reduced temperature condition which were lower by 13.6% than the solar thermal absorber plate and by 0.08% than the PV module respectively. For the unglazed PVT system, it had lower thermal efficiency than the solar thermal absorber plate but higher electrical performance than the PV module due to the cooling effect by the working fluid. However, total efficiency of the glazed PVT system was 72.2% which was higher than combined efficiencies of the solar collector and PV module. Besides, total efficiency of the PVT system would be much higher if calculated based on unit area.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.5
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• pp.43-50
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• 2018

The temperature of underground water generally remains constant regardless of the season. therefore, it is possible to get plenty of energy if we use characteristics of underground water for both cooling and heating. This study evaluates efficiency of real size coaxial and U-tube type complex geothermal system which is combined with underground water well. This study also evaluates relative efficiency/adaptability through comparison with existing geothermal systems(vertical closed loop system, open loop system(SCW)). The heat exchange capacity of complex geothermal system according to temperature difference between circulating water and underground water shows very high significance by increasing proportionally. The temperature change of underground water according to injection energy, shows very high linear growth aspect as injection thermal volume heightens. As a result of evaluation of heat exchange volume between complex geothermal system and comparative geothermal system, coaxial type has 26.1 times greater efficiency than comparative vertical closed type and 2.8 times greater efficiency than SCW type. U-tube type has 26.5 tims greater efficiency than comparative vertical closed type and 2.8 times greater than SCW type as well. This means complex geothermal system has extremely outstanding performance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.4
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• pp.216-223
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• 2006

In this paper, a methodology for the efficiency improvement of the photovoltaic system without adding some elements or increasing the cost comparing with the conventional system is discussed. It is suggested the optimal photovoltaic module configuration through its performance analysis, and also the suitable maximum power point tracking (MPPT) voltage considered the system cost and the efficiency of the converter. The high efficiency photovoltaic system by using the parallel power transfer (PPT) based MPPT converter is proposed and analyzed theoretically comparing with the conventional Buck type MPPT converter. Finally, it is designed and implemented the proposed photovoltaic system for supplying DC 48V by using the PPT based MPPT converter. And the effect of the efficiency improvement and the usefulness of the proposed system is proved through some preliminary simulation and experiment results.