• Journal of Korean Society for Atmospheric Environment
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• v.20 no.5
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• pp.625-632
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• 2004

Perfluorocompounds ($PFC_s$), such as tetrafluoromethane ($CF_4$) and hexafluoroethane ($C_2F_6$), have been widely used as plasma etching and chemical vapor deposition (CVD) gases for semiconductor manufacturing processes. Since these $PFC_s$ are known to cause a greenhouse effect intensively, there has been a growing interest in reducing $PFC_s$ emissions. Among various $CF_4$ decomposing techniques, a dielectric barrier discharge (DBD) is considered as one of a promising candidate because it has been successfully used for generating ozone ($O_3$) and decomposing nitrogen oxide (NO). Firstly, optimal concentration of oxygen for $CF_4$ decomposition was found to figure out how many primary and secondary reactions are associated with DBD process. Secondary, to find effective discharge method for $CF_4$ decomposition, a streamer and a glow mode in DBD are experimentally compared, which includes (i) coaxialcylinder DBD, (ii) DBD reactor packed with glass beads. and (iii) a glow mode operation with a helium gas. The test results showed that optimal concentration of oxygen was ranged 500 ppm~1% for treating 500 ppm of $CF_4$ and helium glow discharge was the most efficient one to decompose $CF_4$.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.267-273
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• 2014

Purpose: This study was conducted to develop a web-based business management system to ensure the efficient operation and transparent management of government-subsidized agricultural machinery rental businesses. Methods: An MS_SQL2000 database management system (DBMS) solution was utilized in the system for high system compatibility and integrated management. This system was targeted to be compatible with Internet Explorer 6.0 or later and to ensure security and seamless web operations. The system administrator is able to manage a fleet of agricultural machinery, including various inventory codes, release and return, fleet registry, and business performance. Users (farmers) may search the database of rental machinery and reserve them. Results: With respect to rental reservations, the system administrator can manage the fleet by setting the rental status to Approved, Released, or Returned. Through the web, the administrator can also create a database that includes machinery specifications, features, and rental rates. In addition, business performance data can be analyzed using a diverse array of tools to streamline the rental business. Without having to go to the rental office, users can save time and money by searching for and renting agricultural machinery through the information available on the website, including availability, specifications, and rental fees. After deploying the system, the time required to analyze monthly performance and create reports was dramatically reduced from 20 days per person to one day per person. Conclusions: Since 2014, AMRB has been installed and is operating in agricultural machinery rental businesses in 31 cities and counties in South Korea. This study recommends continued expansion and dissemination of AMRB for the systematic and efficient management of agricultural machinery rental businesses.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.178-185
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• 2015

Purpose: This research suggests a method of establishing criteria for working area and operating cost for a long-term lease of agricultural machinery. Methods: Eight crops were selected-three food crops and five open-field vegetables-and agricultural machines used for sowing, transplanting, and cultivation in dry-field farming were analyzed. Results: The break-even acreage for agricultural machinery under a long-term lease was found to differ by agricultural machine, ranging from 1.0 to 5.8 ha. In terms of arable land area, the break-even acreages for harvesting machinery and transplanters were 15.6 to 26.1 ha and 6.1 to 8.6 ha, respectively. The working area lessees should secure was divided into two cases: (1) 2.0 to 11.6 ha when leasing individual agricultural machines (sowing and transplanting) for a long-term period, and (2) more than 10 ha when farmers who cultivate beans, potatoes, garlic, onions, and so on lease sowing and transplanting machines as a set. When agricultural machinery was leased for a long term, the operating cost and working time were reduced by 27.6 to 74.4% and 2.5 to 21.6%, respectively, indicating considerable effect. Conclusions: A long-term lease project needs to be promoted to overcome the limitation of short-term leases of agricultural machinery. The local government should lead this project and facilitate the mechanization of dry-field farming. The department in charge of agricultural machinery lease projects needs to set the working area to cover the rate and maintenance cost for farmers who lease agricultural machinery for the long term.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.690-696
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• 2010

Abatement of perfluorocompounds (PFCs) used in semiconductor and display industries has received an attention due to the increasingly stricter regulation on their emission. In order to meet this circumstance, we have developed a radio frequency (RF) driven plasma reactor with multiple annular shaped electrodes, characterized by an easy installment between a processing chamber and a vacuum pump. Abatement experiment has been performed with respect to $CF_4$, a representative PFCs widely used in the plasma etching process, by varying the power, $CF_4$ and $O_2$ flow rates, $CF_4$ concentration, and pressure. The influence of these variables on the $CF_4$ abatement was analyzed and discussed in terms of the destruction & removal efficiency (DRE), measured with a Fourier transform infrared (FTIR) spectrometer. The results revealed that DRE was enhanced with the increase in the discharge power and pressure, but dropped with the $CF_4$ flow rate and concentration. The addition of small quantity of $O_2$ lead to the improvement of DRE, which, however, leveled off and then decreased with $O_2$ flow rate.

• Particle and aerosol research
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• v.14 no.4
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• pp.89-95
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• 2018

People's environmental concerns for fine particles in Korea lead to the strong necessity of improving the performance of environmental control systems. Wet electrostatic precipitators (ESPs) are considered as one of the alternatives to overcome the limit of previous dry ESPs, the re-entrainment of collected particles during rapping and back corona problem for high electrical resistivity dusts etc. In this study, a wire-cylindrical ESP with a thin water film has been developed. Particle collection characteristics were compared in the ESP with operations of water film on and off. Particle collection efficiencies at various applied voltages as well as voltage-current curves were almost the same in the ESP with and without a water film. Particle collection performance for PM1.0, PM2.5 and PM10 in the wet ESP with a water film was constantly maintained with operation time even in the high dust loading environment. This results indicate that a uniform water film in our wet ESP was successfully formed with a very thin layer without any dry spot and therefore could continuously clean the collected particles on the inner wall of the ESP without any performance degradation.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.261-266
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• 2014

Purpose: This study was conducted to serve as a basis for strengthening policy support and R&D to improve the domestic and international competitiveness of domestic agricultural machinery. Levels of satisfaction among farmers and service engineers were analyzed regarding the current quality of agricultural machinery and the primary consumers' propensity for replacement purchases. Methods: A survey was carried out targeting farmers in over 150 townships and 300 villages in South Korea who collectively used 711 tractors, 286 rice transplanters, and 221 combine harvesters. Furthermore, agricultural machinery service engineers from 20 different after-services were surveyed regarding the quality of main components in domestic agricultural machinery versus those in imported agricultural machinery. Results: The farmers' overall quality satisfaction ratings for tractors, rice transplanters, and combine harvesters ranged from 57.1% to 62.6% in consideration of operating performance, failure rate, and durability. Compared with imports, satisfaction ratings for domestic agricultural machinery were 19.1%p to 38.1%p lower for quality. Regarding engines, transmissions, hydraulics, planters, reapers, threshers, and electrical components, only 5.3% to 25.0% of service engineers indicated that domestic agricultural machinery was higher in quality compared with imports. By contrast, 33.3% to 78.9% of those surveyed indicated that domestic components were lower in quality compared with imports. Intent to purchase replacement agricultural machinery at the end of their respective products' lifecycles was indicated that they planned to purchase imported tractors, rice transplanters, and combine harvesters comprised 25.2%, 46.9%, and 43.9%, respectively. This clearly shows that a very high percentage of farmers were satisfied, particularly for transplanters and combine harvesters. Conclusions: The level of desire for purchasing imported agricultural machinery was very high among those who expressed intent to purchase replacement machinery. Therefore, strong policy support and R&D for domestic agricultural machinery is critical for improving competitiveness on the domestic and foreign markets.

• Journal of KSNVE
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• v.10 no.2
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• pp.331-337
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• 2000

The necessity of diagnosis of the rotating machinery which is widely used in the industry is increasing. Many research has been conducted to manipulate field vibration signal data for diagnosing the fault of designated machinery. As the pattern recognition tool of that signal, neural network which use usually back-propagation algorithm was used in the diagnosis of rotating machinery. In this paper, self-organizing feature map(SOFM) which is unsupervised learning algorithm is used in the abnormal defect diagnosis of rotating machinery and then learning vector quantization(LVQ) which is supervised learning algorithm is used to improve the quality of the classifier decision regions.

• Proceedings of the Safety Management and Science Conference
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• 2006.04a
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• pp.447-470
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• 2006

According to Granger causality test, yield of Cooperate Bond and export amount of Machinery have a meaning at statistical Confidence level of 10%. In case of index of the unit cost of export and export amount of Machinery, they have an interactive Granger cause. In yen dollar exchange rate and export amount of Machinery, former variable gives an unilateral Granger cause to latter that. Also, call rate gives an unilateral Granger cause to export amount of Machinery. In case of $M_3$ & export amount of Machinery, former variable have an influence on latter that at 5% Confidence level.

• Journal of Biosystems Engineering
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• v.22 no.3
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• pp.343-350
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• 1997

In farm management, many factors should be considered to select optimum farm machinery Some factors such as fm size can be quantified, but other factors such as working experience can not be. Futhermore, as several factors are missed and assumptions are made for the selection using conventional computer programs, the result is sometimes questionable. This problem can be solved using artificial intelligent techniques such as expert system. In this study, an expert system was developed to select optimum machinery by considering available working days, machinery to on, farming environments, labor cost, population, etc. It also took into account the characteristics of machinery, turning radius, easiness of operation, subsidy, loan to purchase, asset. farmers age, Rest Metabolic Rate, and working experience, etc. Expertise and experience of human experts were utilized to develop the expert system. The developed expert system was evaluated by the human experts and others, and it was proved to be practically useful fir farmers.